Funding for this project from the American Chemical Society Petroleum Research Fund (52488-DNI1) and the University of North Carolina at Greensboro is gratefully acknowledged. We also thank Dr. Terry Nile (UNCG) for loaning us the appropriate glassware for these experiments. Video consulting and editing by Aaron Glancy is also acknowledged.

1. Synthesis of Phenyl HIAT
<ol>
 <li>Equip a dry 100 ml round-bottom flask with a magnetic stirrer and have the flask under an argon atmosphere. Clamp the flask to a stand and place it into a cryogen bath of acetonitrile and solid carbon dioxide pellets. Note: The cryogen should be approximately -45 &deg;C. </li>
 <li>Add 10 ml of dry dichloromethane to the cold flask and allow the solvent to equilibrate to the temperature of the cryogen. Note: The excess headspace in the flask is important for adding diethyl ether later to force precipitation. </li>
 <li>Weigh 0.35 g (1 equiv.) of cyanophenyliodonium triflate and quickly transfer it to the cold flask. Note: The solids should be fairly insoluble at this temperature. </li>
 <li>Tare the mass of an empty syringe and then use it weigh 0.37 g (1 equiv.) of phenylethynyltributyltin.</li>
 <li>Inject the phenylethynyltributyltin into the cold solution. Note: The dissolution of solids is an indication that the HIAT has been formed. The approximate time for dissolution is 30 min. </li>
 <li>Add diethyl ether and hexane to force precipitation of the product. Note: If a precipitate does not form, evaporate the solvent under reduced pressure and add a mixture of diethyl ether and hexane to force precipitation of the HIAT.</li>
 <li>Equip a vacuum flask with a B&uuml;chner funnel and pour the solution onto the funnel for filtration.</li>
 <li>Collect the solids and store cold in an opaque container. </li>
</ol>
2. Synthesis of n-Pentyl HIAT
<ol>
 <li>Equip a dry 250 ml three-necked round-bottom flask with a magnetic stirrer and have the flask under an argon atmosphere. Clamp the flask to a stand and place it into a cryogen bath of acetonitrile and solid carbon dioxide pellets. Note: The cryogen should be approximately -45 &deg;C. </li>
 <li>Assemble a Schlenk filtration apparatus on the flask so that the filtration can be performed quickly and at a cold temperature. Grease and clamp together each joint of the apparatus. Note: The filtration system can be constructed by several means but it is important that the system has the capability to push with inert gas and pull with a vacuum through a glass filter. </li>
 <li>Add 10 ml of dry dichloromethane to the cold flask and allow the solvent to equilibrate to the temperature of the cryogen. Note: The excess headspace in the flask is important for adding hexane later to force precipitation.</li>
 <li>Weigh 0.35 g (1 equiv.) of cyanophenyliodonium triflate and quickly transfer it to the cold flask. Note: The solids should be fairly insoluble at this temperature. </li>
 <li>Tare the mass of an empty syringe and then use it weigh 0.44 g (1 equiv.) of tributyltin heptyne.</li>
 <li>Inject the tributyltin heptyne into the cold solution. Note: The dissolution of solids is an indication that the HIAT has been formed. The approximate time for dissolution is 30 min. </li>
 <li>Inject 75 ml of hexane into the extra headspace of the flask to form a precipitate. </li>
 <li>Place the collection flask under vacuum. </li>
 <li>Unclamp the apparatus from the stand and carefully tilt it to pour the solution onto the glass filter. Open the collection flask vacuum to pull the liquid through. Note: Do not allow the vacuum to pull air into the vessel.</li>
 <li>Dismantle the apparatus and scrape the solids off the filter once the filtration is complete. Once the solid is removed from the filtrate it is less air and temperature sensitive and can be handled open to air. </li>
 <li>Collect the solids and store cold in an opaque container. </li>
</ol>
3. O-H Insertion of Cyanocarbenes Made from Phenyl HIAT
<ol>
 <li>Equip a dry 50 ml round-bottom flask with a magnetic stirrer and have the flask under an argon atmosphere. Clamp the flask to a stir plate and inject 20 ml of dry methanol to the flask. </li>
 <li>Weigh 0.300 g (1 equiv.) of the previously synthesized Phenyl HIAT and quickly add it to the flask.</li>
 <li>Add 0.047 g (1 equiv.) of sodium azide to the flask. Note: The solution will darken over time and nitrogen gas is generated by cyanocarbene formation. </li>
 <li>Let the reaction continue for as long as bubble formation occurs. The approximate time for completion is 20 min. </li>
 <li>Expose the solution to air and evaporate the solvent using reduced pressure. </li>
 <li>Add dichloromethane to the residual liquid and perform aqueous extraction to remove the sodium triflate. Collect the organic phases of dichloromethane and dry with anhydrous sodium sulfate. </li>
 <li>Decant the solution and evaporate using reduced pressure. </li>
 <li>Perform column chromatography to purify the cyanocarbene product. </li>
</ol>
4. Cyclopropanation Cyanocarbene Reaction Using Phenyl HIAT
<ol>
 <li>Weigh 0.125 g (1 equiv.) of tetrabutylammonium azide in a glovebox and place it in a dry 10 ml round-bottom flask equipped with a magnetic stirrer.</li>
 <li>Cap the 10 ml round-bottomed flask containing the tetrabutylammonium azide, remove it from the glovebox, and place it on a stir plate under argon gas using a Schlenk line. </li>
 <li>Add 1.0 ml of styrene to the flask and allow the flask to stir. Note: The azide does not need to dissolve. </li>
 <li>Quickly add 0.200 g (1 equiv.) of Phenyl HIAT to this slurry and place the septum back on the flask that is connected to a Schlenk line. Note: The solution should immediately darken and generate nitrogen gas by cyanocarbene formation. </li>
 <li>Allow the reaction to continue for as long as bubble formation occurs. The approximate time for completion is one minute. </li>
 <li>After the bubbles have stopped, expose the solution to air and perform column chromatography to purify the product. </li>
</ol>

<ol>
	<li>Hyatt, I. F. D., Meza-Avi&#241;a, M. E., Croatt, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alkynes+&amp;+Azides:+Not+Just+for+Click+Reactions.">Alkynes &amp; Azides: Not Just for Click Reactions.</a> Synlett. 23 (20), 2869-2874 (2012).</li><li>Meza-Avi&#241;a, M. E., Patel, M. K., Lee, C. B., Dietz, T. J., Croatt, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+Formation+of+1,5-Substituted+Sulfonyl+Triazoles+Using+Acetylides+and+Sulfonyl+Azides.">Selective Formation of 1,5-Substituted Sulfonyl Triazoles Using Acetylides and Sulfonyl Azides.</a> Organic Letters. 13 (12), 2984-2987 (2011).</li><li>Hyatt, I. F. D., Croatt, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactions+of+Hypervalent+Iodonium+Alkynyl+Triflates+with+Azides:+Generation+of+Cyanocarbenes.">Reactions of Hypervalent Iodonium Alkynyl Triflates with Azides: Generation of Cyanocarbenes.</a> Angewandte Chemie International Edition. 51 (30), 7511-7514 (2012).</li><li>Banert, K., Hagedorn, M., Wutke, J., Ecorchard, P., Schaarschmidt, D., Lang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elusive+ethynyl+azides:+trapping+by+1,3-dipolar+cycloaddition+and+decomposition+to+cyanocarbenes.">Elusive ethynyl azides: trapping by 1,3-dipolar cycloaddition and decomposition to cyanocarbenes.</a> Chemical Communications. 46 (23), 4058-4060 (2010).</li><li>Koumbis, A., Kyzas, C., Savva, A., Varvolis, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+New+Alkynyl(phenyl)iodonium+Salts+and+Their+Use+in+the+Synthesis+of+Phenylsulfonyl+Indenes+and+Acetylenes.">Formation of New Alkynyl(phenyl)iodonium Salts and Their Use in the Synthesis of Phenylsulfonyl Indenes and Acetylenes.</a> Molecules. 10 (10), 1340-1350 (2005).</li><li>Banert, K., Arnold, R., Hagedorn, M., Thoss, P., Auer, A. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alkynyl-+and+Alkenyl(phenyl)iodonium+Compounds.">Alkynyl- and Alkenyl(phenyl)iodonium Compounds.</a> Angewandte Chemie International Edition. 31 (3), 274-285 (2003).</li><li>Hembre, R. T., Scott, C. P., Norton, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conversion+of+olefins+to+ditriflates+by+&#956;-oxobis[(trifluoromethanesulfonato)(phenyl)iodine.">Conversion of olefins to ditriflates by &#956;-oxobis[(trifluoromethanesulfonato)(phenyl)iodine.</a> Journal of Organic Chemistry. 52 (16), 3650-3654 (1987).</li><li>Stang, P. J., Surber, B. W., Chen, Z., Roberts, K. A., Anderson, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acetylenic+Esters.+Preparation+and+Mechanism+of+Formation+of+Alkynyl+Tosylates+and+Mesylates+via+Tricoordinate+Iodonium+Species.">Acetylenic Esters. Preparation and Mechanism of Formation of Alkynyl Tosylates and Mesylates via Tricoordinate Iodonium Species.</a> Journal of the American Chemical Society. 109 (1), 228-235 (1987).</li><li>Zhdankin, V. V., Crittell, C. M., Stang, P. J., Zefirov, N. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+general+approach+to+unsymmetrical+tricoordinate+iodinanes:+Single+step+preparation+of+mixed+iodosobenzene+sulfonates+Phl(X)OSO2R,+via+reaction+of+iodosobenzene+with+Me3SiX.">A general approach to unsymmetrical tricoordinate iodinanes: Single step preparation of mixed iodosobenzene sulfonates Phl(X)OSO2R, via reaction of iodosobenzene with Me3SiX.</a> Tetrahedron Letters. 31 (34), 4821-4824 (1990).</li><li>Lee, H., Jung, Y., Yoon, Y., Kim, B. G., Kim, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Angularly+Fused+Triquinanes+from+Linear+Substrates+through+Trimethylenemethane+Diyl+[2+++3]+Cycloaddition+Reaction.">Angularly Fused Triquinanes from Linear Substrates through Trimethylenemethane Diyl [2 + 3] Cycloaddition Reaction.</a> Organic Letters. 12 (11), 2672-2674 (2010).</li><li>Beauchard, A., Phillips, V. A., Lloyd, M. D., Threadgill, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+2-(4-carboxybutenyl)-+and+2-(4-carboxybutynyl)-cyclopentene-1-carboxamides.">Synthesis of 2-(4-carboxybutenyl)- and 2-(4-carboxybutynyl)-cyclopentene-1-carboxamides.</a> Tetrahedron. 65 (39), 8176-8184 (2009).</li><li>Kitamura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Alternative+Synthesis+of+Alkynyl(phenyl)iodonium+Triflates+Using+(Diacetoxyiodo)benzene+and+Alkynylsilanes.">An Alternative Synthesis of Alkynyl(phenyl)iodonium Triflates Using (Diacetoxyiodo)benzene and Alkynylsilanes.</a> Synthesis. 10, 1416 (1998).</li><li>Bouma, M. J., Olofsson, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+One-Pot+Synthesis+of+Alkynyliodonium+Salts+and+Alkynyl+Benziodoxolones+from+Aryl+Iodides.">General One-Pot Synthesis of Alkynyliodonium Salts and Alkynyl Benziodoxolones from Aryl Iodides.</a> Chemistry A European Journal. 18, 14242 (2012).</li><li>Williamson, B. L., Stang, P. J., Preparation Arif, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+Structure,+and+Diels-Alder+Cycloaddition+Chemistry+of+&#946;-Functionalized+Alkynyl(phenyl)iodonium+Salts.">Molecular Structure, and Diels-Alder Cycloaddition Chemistry of &#946;-Functionalized Alkynyl(phenyl)iodonium Salts.</a> Journal of the American Chemical Society. 115 (7), 2590-2597 (1993).</li></ol>

The authors declare that they have no competing financial interests.

Hypervalent iodonium alkynyl triflates, or HIATs, are formed and can be reacted with azide sources to form cyanocarbenes. It is very important that all necessary precautions are taken since many of the reagents and intermediates shown in this video are potentially explosive and highly toxic. Although the high level of reactivity can be dangerous if ill-prepared, it is shown in this video that the inherent reactivity of the compounds can be harnessed by capturing the cyanocarbenes in various reactions such as O-H insert...

The continued evolution of organic chemistry hinges on the design and development of new reactions. In particular, the discovery of new reactions that enable previously unimaginable synthetic routes bear ultimate significance. Towards this end, our group desired to convert two carbons of an alkyne and a nitrogen of an azide into a cyanocarbene.1 This previously unknown transformation would allow for a significant increase in molecular complexity since the reactive cyanocarbene would rapidly react further. The initial effort was to use a nucleophilic alkyne and electrophilic azide, but triazoles were efficiently formed in this case as opposed to cyanocarbenes.2 Using an umpolung approach, the second method uses an electrophilic alkyne and nucleophilic azide and products resulting from cyanocarbene reactions are fortunately formed in this case.3 There are many sources of nucleophilic azide, however, electrophilic alkynes are much less common. The group of Klaus Banert previously reported the proof-of-concept for this reaction using an alkynyl-chloride,4 but our group and the Banert group independently and contemporaneously determined that hypervalent iodonium alkynyl triflates (HIATs) are much better electrophiles for the reasons of stability and reactivity.3,6 We herein describe the synthesis, isolation, and reaction of these HIATs with azides to form and react in situ as cyanocarbenes.
Several safety precautions should be considered before proceeding with these experiments. Some hypervalent iodonium alkynyl triflates are unstable and will decompose, sometime violently, when exposed to air and light.7 To form the cyanocarbene intermediate, the procedure requires the use of azide sources. Azides are explosive and highly toxic.8 Proper personal protection equipment should be worn when handling these materials, especially organotin, and all manipulation of the reagents should take place in properly ventilated hoods. The cyanocarbene is a powerful and unstable reactive intermediate. Take care to perform experiments initially on small scales so that nitrogen gas evolution is controllable and never perform these reactions in closed systems. If scale-up of the reaction is desired, we strongly suggest the use of a safety shield.
The synthesis of many HIATs have been previously published including the use of Zefirov's reagent9,10, and Koser's reagent,9,11 however, this video will be using the cyanophenyliodonium triflate reagent9,12 (Figure 1). Cyanophenyliodonium triflate was synthesized based on a previously reported literature preparation displayed.13 The reagent reacts with trialkyl-tin modified alkynes14 to form the desired product. After the HIAT is synthesized and isolated it can be reacted with azide to form a reactive cyanocarbene intermediate (Figure 2). There are several other methods that can be used to synthesize the iodonium alkynes such as using alkynyl silanes15 and alkynyl boronic esters16 but the method in the video was chosen because, in our experience, it had better efficiency and yield.
Our proposed mechanism3,5 (Figure 3) for this reaction involves the addition of an azide source to the &beta;-carbon of the alkyne, thereby forming an iodo-ylide which decomposes to iodobenzene and a vinylidene-carbene. The vinylidene-carbene can then undergo a 1,2-rearrangement via migration of either the R-group or azide to afford an alkynyl-azide. The alkynyl-azide then extrudes dinitrogen to form a cyanocarbene which can react with a substrate. It should be noted that there can be formation of a hypervalent iodonium alkenyl triflate species, depending on conditions. The by-product is favored at lower temperatures in protic solvents where the protonation of the iodo-ylide is faster than the rearrangement to the alkynyl azide. Another possible product that occurs during O-H insertion reactions is a vinyl ether where the vinylidene-carbene is trapped before the rearrangement to the alkynyl-azide can occur. The propensity to form this vinyl ether is determined by the R group. 
One of the main advantages of this reaction is that after the carbene reacts, the resultant nitrile group is a convenient handle for further functionalization. Many synthons can be envisioned with this method and different products can be formed with the same substrates. Controlling the product mixture with temperature, concentration, and the R group of the alkyne is necessary.3 With proper insight upon how cyanocarbenes behave, the method shows a viable means to quickly adding chemical complexity to form a targeted molecule. Examples of how the cyanocarbene reacts include O-H insertion where the nucleophilic oxygen atom of the alcohol attacks the carbene and then proton transfer occurs, dimethyl sulfoxide complexation, where the carbene combines with the sulfur atom, and cyclopropanation where the carbene reacts with an alkene.

<table border="1">
<tbody>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Reagent</td>
 </tr>
 <tr>
 <td>Phenyl acetylene</td>
 <td>Acros</td>
 <td>AC152461000</td>
 <td></td>
 </tr>
 <tr>
 <td>Tri-n-butyltin chloride</td>
 <td>Acros</td>
 <td>139351000</td>
 <td></td>
 </tr>
 <tr>
 <td>Lithium bis(trimethysilyl)amide</td>
 <td>Acros</td>
 <td>347701000</td>
 <td></td>
 </tr>
 <tr>
 <td>Iodobenzene diacetate</td>
 <td>Acros</td>
 <td>176560250</td>
 <td></td>
 </tr>
 <tr>
 <td>Trimethylsilyl cyanide</td>
 <td>Aldrich</td>
 <td>212849</td>
 <td>Extremely toxic. Handle this chemical only in an adequately ventilated hood with extreme caution.</td>
 </tr>
 <tr>
 <td>Trimethylsilyl triflate</td>
 <td>Alfa Aesar</td>
 <td>A12535</td>
 <td></td>
 </tr>
 <tr>
 <td>Sodium Azide</td>
 <td>Sigma-Aldrich</td>
 <td>S8032</td>
 <td>Shock sensitive.</td>
 </tr>
 <tr>
 <td>Tetrabutylammonium azide</td>
 <td>Aldrich</td>
 <td>651664</td>
 <td>If possible, store and handle in a glovebox due to this compound's hygroscopic nature.</td>
 </tr>
 <tr>
 <td>1-Heptyne</td>
 <td>Acros</td>
 <td>223460250</td>
 <td></td>
 </tr>
 <tr>
 <td>Styrene</td>
 <td>Aldrich</td>
 <td>240869</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>[header]</td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Material</td>
 </tr>
 <tr>
 <td>Rotary Evaporator (Hei-VAP)</td>
 <td>Heidolph</td>
 <td>517-61000-01-0</td>
 <td></td>
 </tr>
 <tr>
 <td>Glovebox</td>
 <td>MBRAUN</td>
 <td>UL-018</td>
 <td></td>
 </tr>
 </tbody>
</table>

synthesis of hypervalent iodonium alkynyl triflates for the application of generating cyanocarbenes

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent reactions with azides to form cyanocarbene intermediates. The synthesis of hypervalent iodonium alkynyl triflates can be facile, but difficulties stem from their isolation and reactivity. In particular, the necessity to use filtration under inert atmosphere at -45 &deg;C for some HIATs requires special care and equipment. Once isolated, the compounds can be stored and used in reactions with azides to form cyanocarbene intermediates. 
The evidence for cyanocarbene generation is shown by visible extrusion of dinitrogen as well as the characterization of products that occur from O-H insertion, sulfoxide complexation, and cyclopropanation. A side reaction of the cyanocarbene formation is the generation of a vinylidene-carbene and the conditions to control this process are discussed. There is also potential to form a hypervalent iodonium alkenyl triflate and the means of isolation and control of its generation are provided. The O-H insertion reaction involves using a HIAT, sodium azide or tetrabutylammonium azide, and methanol as solvent/substrate. The sulfoxide complexation reaction uses a HIAT, sodium azide or tetrabutylammonium azide, and dimethyl sulfoxide as solvent. The cyclopropanations can be performed with or without the use of solvent. The azide source must be tetrabutylammonium azide and the substrate shown is styrene.

Figure 1 illustrates the synthesis of a HIAT by using cyanophenyliodonium alkynyl triflate. The HIAT can then be used to generate cyanocarbenes which will undergo O-H insertion of cyclopropanation. The O-H insertion reaction with Phenyl HIAT produces 2-methoxy-2-phenylacetonitrile in up to a 75% yield. The cyclopropanation reaction with Phenyl HIAT produces 1,2-diphenylcyclopropanecarbonitrile in up to a 61% yield. Although not demonstrated in the video, dimethyl sulfoxide complexation can occur with the...

Watch this Scientific Journal Video about Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes at JoVE.com

Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes

Herein is described the synthesis, isolation, and reactions of hypervalent iodonium alkynyl triflates (HIATs) with azides to generate cyanocarbenes. The procedures will involve air-sensitive and cryogen techniques, including cold filtration under an inert atmosphere. Handling and safety of the synthesized compounds will also be discussed.

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent ...

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10.8K Views.  University of North Carolina at Greensboro. Herein is described the synthesis, isolation, and reactions of hypervalent iodonium alkynyl triflates (HIATs) with azides to generate cyanocarbenes. The procedures will involve air-sensitive and cryogen techniques, including cold filtration under an inert atmosphere. Handling and safety of the synthesized compounds will also be discussed.

Video: Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

The development of fluorescent indicators represented a revolution for life sciences. Genetically encoded and synthetic fluorophores with sensing abilities allowed the visualization of biologically relevant species with high spatial and temporal resolution. Synthetic dyes are of particular interest thanks to their high tunability and the wide range of measureable analytes. However, these molecules suffer several limitations related to small molecule behavior (poor solubility, difficulties in targeting, often no ratiometric imaging allowed). In this work we introduce the development of dendrimer-based sensors and present a procedure for pH measurement in vitro, in living cells and in vivo. We choose dendrimers as ideal platform for our sensors for their many desirable properties (monodispersity, tunable properties, multivalency) that made them a widely used scaffold for several biomedical devices. The conjugation of fluorescent pH indicators to the dendrimer scaffold led to an enhancement of their sensing performances. In particular dendrimers exhibit reduced cell leakage, improved intracellular targeting and allow ratiometric measurements. These novel sensors were successfully employed to measure pH in living HeLa cells and in vivo in mouse brain.

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

Fluorescence sensors are powerful tools in life science. Here we describe a methodology to synthesize and use dendrimer-based fluorescent sensors to measure pH in living cells and in vivo. The dendritic scaffold enhances the properties of conjugated fluorescent dyes leading to improved sensing properties.

The development of  fluorescent indicators represented a revolution for life sciences. Genetically  encoded and synthetic fluorophores with sensing ...

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are rapidly oxidized, for example by atmospheric oxygen, to indigo type dyes. This reaction enables fast and easy screening in vivo without isolation or purification of enzymes, as well as rapid tests on agar plates or in solution (e.g., blue-white screening, micro-wells) and is used in biochemistry, histochemistry, bacteriology and molecular biology. Unfortunately the synthesis of such substrates proved to be difficult, due to various side reactions and the low reactivity of the indoxyl hydroxyl function. Especially for glucose type structures low yields were observed. Our novel approach employs indoxylic acid ester as key intermediates. Indoxylic acid esters with varied substitution patterns were prepared on scalable pathways. Phase transfer glycosylations with those acceptors and peracetylated glycosyl halides can be performed under common conditions in high yields. Ester cleavage and subsequent mild silver mediated glycosylation yields the peracetylated indoxyl glycosides in high yields. Finally deprotection is performed according to Zempl&#233;n.

Indoxyl glycosides are well-established and widely used tools for enzyme screening and enzyme activity monitoring. Especially for glucose type structures previous syntheses proved to be challenging and low yielding. Our novel approach employs indoxylic acid esters as precious intermediates to yield a considerable number of indoxyl glycosides in good yields.

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

Synthesis of Zeolites Using the ADOR (Assembly-Disassembly-Organization-Reassembly) Route

Zeolites are an important class of materials that have wide ranging applications such as heterogeneous catalysts and adsorbents which are dependent on their framework topology. For new applications or improvements to existing ones, new zeolites with novel pore systems are desirable. We demonstrate a method for the synthesis of novel zeolites using the ADOR route. ADOR is an acronym for Assembly, Disassembly, Organization and Reassembly. This synthetic route takes advantage of the assembly of a relatively poorly stable that which can be selectively disassembled into a layered material. The resulting layered intermediate can then be organized in different manners by careful chemical manipulation and then reassembled into zeolites with new topologies. By carefully controlling the organization step of the synthetic pathway, new zeolites with never before seen topologies are capable of being synthesized. The structures of these new zeolites are confirmed using powder X-ray diffraction and further characterized by nitrogen adsorption and scanning electron microscopy. This new synthetic pathway for zeolites demonstrates its capability to produce novel frameworks that have never been prepared by traditional zeolite synthesis techniques.

Synthesis of Zeolites Using the ADOR Assembly-Disassembly-Organization-Reassembly Route

A protocol for the preparation of novel zeolites by the ADOR (Assembly-Disassembly-Organization-Reassembly) synthetic route is presented.

Zeolites are an important class of materials that have wide ranging applications such as heterogeneous catalysts and adsorbents which are dependent on ...

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of trifluoromethoxylated aromatic compounds remains a formidable challenge in organic synthesis. Conventional approaches often suffer from poor substrate scope, or require use of highly toxic, difficult-to-handle, and/or thermally labile reagents. Herein, we report a user-friendly protocol for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate using 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one (Togni reagent II). Treating methyl 4-(N-hydroxyacetamido)benzoate (1a) with Togni reagent II in the presence of a catalytic amount of cesium carbonate (Cs2CO3) in chloroform at RT afforded methyl 4-(N-(trifluoromethoxy)acetamido)benzoate (2a). This intermediate was then converted to the final product methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) in nitromethane at 120 &#176;C. This procedure is general and can be applied to the synthesis of a broad spectrum of ortho-trifluoromethoxylated aniline derivatives, which could serve as useful synthetic building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and functional materials.

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

Synthesis and Mass Spectrometry Analysis of Oligo-peptoids

Peptoids are sequence-controlled peptide-mimicking oligomers consisting of N-alkylated glycine units. Among many potential applications, peptoids have been thought of as a type of molecular information storage. Mass spectrometry analysis has been considered the method of choice for sequencing peptoids. Peptoids can be synthesized via solid phase chemistry using a repeating two-step reaction cycle. Here we present a method to manually synthesize oligo-peptoids and to analyze the sequence of the peptoids using tandem mass spectrometry (MS/MS) techniques. The sample peptoid is a nonamer consisting of alternating N-(2-methyloxyethyl)glycine (Nme) and N-(2-phenylethyl)glycine (Npe), as well as an N-(2-aminoethyl)glycine (Nae) at the N-terminus. The sequence formula of the peptoid is Ac-Nae-(Npe-Nme)4-NH2, where Ac is the acetyl group. The synthesis takes place in a commercially available solid-phase reaction vessel. The rink amide resin is used as the solid support to yield the peptoid with an amide group at the C-terminus. The resulting peptoid product is subjected to sequence analysis using a triple-quadrupole mass spectrometer coupled to an electrospray ionization source. The MS/MS measurement produces a spectrum of fragment ions resulting from the dissociation of charged peptoid. The fragment ions are sorted out based on the values of their mass-to-charge ratio (m/z). The m/z values of the fragment ions are compared against the nominal masses of theoretically predicted fragment ions, according to the scheme of peptoid fragmentation. The analysis generates a fragmentation pattern of the charged peptoid. The fragmentation pattern is correlated to the monomer sequence of the neutral peptoid. In this regard, MS analysis reads out the sequence information of the peptoids.

A protocol is described for the manual synthesis of oligo-peptoids followed by sequence analysis by mass spectrometry.

Peptoids are sequence-controlled peptide-mimicking oligomers consisting of N-alkylated glycine units. Among many potential applications, peptoids have ...