Los autores desean reconocer la Universidad de Vanderbilt y el Instituto de Biología química para apoyo financiero. Sr. Ellis de Berkley y Prof. John McLean son reconocidos por análisis espectral de masa de alta resolución.

1. representante de microonda-asistida Desnitruración
<ol><li>Coloque el éster de nitrato azido (1.0 equiv, 0,2 mmol) en un frasco de reacción de microondas de 8 mL. La magnitud de la reacción se puede aumentar a varios mmol sin ningún efecto adverso sobre el progreso de la reacción.</li>
	<li>El éster de azido-nitrato en acetona al 20% AQ (0,1 M, 2,0 mL) se disuelven. Añadir piridina (5,0 equivalente, 0,08 mL, 1,0 mmol) en el recipiente de la reacción. La tapa del frasco de irradiación de microondas y colocar el recipiente de la reacción en una cavidad de reactor de microondas.</li>
	<li>Irradiar la solución a 120 ° C durante 15 min con agitación y con un tiempo de espera fijo. El tiempo de espera representa cuánto se producirá la irradiación a la temperatura señalada y la presión resultante. Calentar todas las reacciones a la temperatura divulgada durante un período de rampa de 2 minutos. Controlar la temperatura con un sensor incorporado IR.</li>
	<li>Después de 15 min, analizar la mezcla de reacción mediante cromatografía en capa fina (TLC) para confirmar el consumo de material de partida. Utilizar acetato de etilo/hexanes 1:1 como eluyente.<ol>
<li>Visualizar la placa de TLC mediante tinción de molybate de amonio cérico. Rf del reactivo y del producto variarán, pero el alcohol reducción es generalmente 0.05 a 0.1 menor Rf que el reactivo.</li>
	</ol>
</li>
</ol>2. formación de la trichloroacetimidate
<ol><li>Tras consumo completo de material de partida, se evapora el disolvente a un volumen reducido con una línea aérea. Luego diluir con (diclorometano) CH2Cl2 (1,0 mL) y utilizar una jeringa para eliminar la capa de agua. Una vez retirada la capa de agua, enfriar la mezcla de reacción a 0 ° C usando un baño de agua helada.</li>
	<li>A continuación, añadir DBU (eq 10, 0.3 mL, 1,9 mmol) y 2,2,2-trichloroacetonitrile (50 eq, 1,0 mL, 10 mmol) en el recipiente de la reacción. Se añaden dos reactivos en exceso y se necesita un mínimo de 1 equivalente de base y 1 equivalente de 2,2,2-trichloroacetonitrile.</li>
	<li>Deje que la mezcla de reacción agitar y calentar a temperatura ambiente. Vigilar la reacción por el TLC para confirmar el consumo de material de partida.<ol>
<li>Utilizar acetato de etilo/hexanes 1:1 como eluyente. Visualizar la placa de TLC mediante tinción de molybate de amonio cérico. Rf del reactivo y del producto variará.</li>
	</ol>
</li>
	<li>Después de la consumición completa del material de partida, transferir la mezcla de reacción a un matraz de recuperación y concentrar la mezcla en vacío a 30 ° C. Evaporación del disolvente proveerá un crudo amarillo pálido a marrón aceite.</li>
	<li>Purifique el producto crudo por cromatografía de columna de gel de silicona con una columna de cromatografía de 1,5 cm y de 1:4 acetato de etilo/hexanes como eluyente. La forma física de la imidate variará de molécula a molécula.</li>
</ol><img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56610/56610fig1v3.jpg"> Figura 1. Ejemplos representativos de la conversión de un pote de ésteres de 2-azido-1-nitrato al 2-azido-1-trichloroimidates. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig1v3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>

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Los autores tienen intereses financieros que compiten.

El protocolo descrito en este tutorial proporciona un método para convertir ésteres de nitrato a la funcionalidad útil, reactiva. En un sentido más amplio, empleando un reactor de microondas para completar maniobras específicas en el transcurso de una síntesis de hidratos de carbono tiene el potencial para hacer transformaciones difíciles fáciles y rutinarias. Nuestro objetivo en este tutorial es demostrar cómo manejar los hidratos de carbono en el contexto de la irradiación de microondas.
En el caso de la reacción de los padres, los esfuerzos anteriores para lograr Desnitruración típicamente han confiado en reactivos fuertemente nucleofílico y prolongado tiempo de reacción. La fuerza de la tecnología descrita en este documento es que el microondas proporciona calefacción de alta potencia en un intervalo muy corto, permitiendo la manipulación cuantitativa de un éster de nitrato anomérico. Hasta el momento, el método funciona mejor con compuestos que son glucosa configurada en C2 es decir alcohol "Ecuatorial" en esta posición. Compuestos que disponen de configuración de la manosa "axial" en C2 deben ser sometidos a irradiación prolongada, ya que son resistentes a la hidrólisis. Mientras que la reacción se lleva a cabo en presencia de base para secuestrar el ácido producido en la nitración de, base puede ser excluida para las moléculas que no son ácidas lábiles. Por otra parte, tiempos de reacción puede incrementarse para hidrolizar las moléculas que son resistentes a la reacción (es decir, azúcares peracetylated). En cuanto a la purificación, puede purificar el alcohol producido después de la reacción de microondas.

Debido a su ubicuidad en biología molecular, hidratos de carbono han sido objetivos de larga data para síntesis química. 1 , 2 , 3 en la base de cualquier campaña sintético es el correcto despliegue de reacciones de glicosilación para construir la cadena de oligosacáridos. 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 no es de extrañar, hay un gran número de métodos para instalar enlaces glucosídicos. 13 , 14 Koenigs-Knorr el método es uno de los procedimientos lo más temprano posible conocidos e implica una glicosil cloruro o bromuro de acoplamiento con un componente alcohólico, generalmente bajo activación de metales pesados (mercurio o plata). 15 fluoruros glycosyl relacionados primero fueron introducidos como donantes en 1981 por el grupo de Mukaiyama y han encontrado uso extenso debido a su mayor estabilidad térmica y química. 16 en el extremo opuesto del espectro de reactividad son glicosil yoduros, que son mucho más reactivos que los otros halides. Mayor reactividad se acompaña de stereocontrol creciente, particularmente cuando formando α-linked oligosacáridos. 17 además de "haloglycosides", thioglycosides han encontrado gran utilidad, en parte, debido a su facilidad de formación, estabilidad a una multitud de condiciones de reacción y la activación con los reactivo electrofílico. 18
Los métodos descritos anteriormente foco sobre la conversión de un alcohol anomérico a un "sin oxígeno" que contiene, latente dejando el grupo que está activado y finalmente desplazada por un alcohol de una molécula aceptora. Activación de oxígeno anomérico descrito por la escuela Schmidt, se centra en convertir el oxígeno de C1, a un grupo dejando. 19 este método es el más potente y ampliamente utilizado en las reacciones químicas glicosilación. Los donantes Trichloroacetimidate se preparan fácilmente de un azúcar reductor y trichloroacetonitrile en presencia de una base como el carbonato de potasio (K2CO3) o 1, 8-Diazabiciclo [5.4.0] undéc-7-eno (DBU). Estas especies se activan utilizando ácidos de Lewis. 20
Recientemente, nos han informado que los donantes 2-azido-1-trichloroacetimidate se pueden preparar directamente de glycals. El proceso implica una reacción en dos, uno de otro procedimiento de los ésteres de 2-azido-1-nitrato. 21 este protocolo detallado está diseñado para ayudar a los profesionales para completar con éxito la transformación de alto rendimiento. De particular interés es el primer paso de la secuencia, que se centra en térmica Desnitruración en microondas - asistida por calefacción. También esperamos proporcionar un tutorial visual en el empleo de reactores de microondas en síntesis orgánica.

<table>
	<tbody>
		<tr>
			<td>230 400 mesh silica gel</td>
			<td>SiliCycle Inc</td>
			<td>R10030B</td>
			<td></td>
		</tr>
		<tr>
			<td>TLC plates</td>
			<td>SiliCycle Inc</td>
			<td>TLG-R10014B-527</td>
			<td></td>
		</tr>
		<tr>
			<td>Ceric ammonium molybdate</td>
			<td>Sigma-Aldrich</td>
			<td>A1343</td>
			<td></td>
		</tr>
		<tr>
			<td>Solvent Still</td>
			<td>Mbraun</td>
			<td>MB-SPS-800</td>
			<td></td>
		</tr>
		<tr>
			<td>Infared spectrometer</td>
			<td>Thermo</td>
			<td>Thermo Electron IR100</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclear Magnetic Resonance</td>
			<td>Bruker</td>
			<td></td>
			<td>400, 600 MHz</td>
		</tr>
		<tr>
			<td>LC/MS</td>
			<td>Thermo/Dionex</td>
			<td></td>
			<td>Single quad, ESI</td>
		</tr>
		<tr>
			<td>HRMS</td>
			<td>Agilent</td>
			<td>Synapt G2 S HDMS</td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave reactor</td>
			<td>Anton Parr</td>
			<td>Anton Parr G10 Monowave 200</td>
			<td></td>
		</tr>
		<tr>
			<td>DBU</td>
			<td>Sigma-Aldrich</td>
			<td>139009</td>
			<td></td>
		</tr>
		<tr>
			<td>CCl3CN</td>
			<td>Sigma-Aldrich</td>
			<td>T53805</td>
			<td></td>
		</tr>
		<tr>
			<td>Pyridine</td>
			<td>Sigma-Aldrich</td>
			<td>270970</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Fisher Scientific</td>
			<td>A18-20</td>
			<td>Tech. grade</td>
		</tr>
		<tr>
			<td>Phase separator</td>
			<td>Biotage</td>
			<td>120-1901-A</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotary evaporator</td>
			<td>Buchi</td>
			<td>R-100</td>
			<td></td>
		</tr>
	</tbody>
</table>

one-pot microwave-assisted conversion of anomeric nitrate-esters to trichloroacetimidates

El objetivo de este procedimiento es proporcionar una demostración de la conversión de un pote de un 2-azido-1-nitrato-éster a un donante de glicosil trichloroacetimidate. Después de azido-nitración de un glycal, puede hidrolizar el éster 2-azido-1-nitrato de producto bajo irradiación de microondas-asistida. Esta transformación se logra utilizando reactivos fuertemente nucleofílico y prolongado tiempo de reacción. Irradiación de microondas induce la hidrólisis, en la ausencia de reactivos, tiempos de reacción cortos. Tras Desnitruración, el alcohol intermedio anomérico se convierte, en la misma olla, a la 2-azido-1-trichloroacetimidate correspondiente.

La tecnología descrita fue demostrada en un grupo de tres ésteres de 2-azido-1-nitrato. En cada caso el primer paso de la reacción era completado dentro de 20 minutos.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56610/56610fig2v3.jpg"> Figura 2. Ejemplo de hidrólisis (1 ->2) y la conversión de un pote de ester 2-azido-1-nitrato de 1 (1->3). <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig2v3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
(2S,3R,4S,5S,6R)-2-(((2R,3S,4R,5R,6R)-4-acetoxy-2-(acetoxymethyl)-5-azido-6-(imino(2l3-trichloran-2-yl)methoxy)tetrahydro-2H-pyran-3-yl)oxy)-6-(acetoxymethyl)tetrahydro-2H-pyran-3,4,5-triyl triacetato (3) Una mezcla de 11:1:6 (manno - alfa / alfa gluco-/ beta gluco-) configurado azidonitrate ésteres 1 (1,0 equiv, 0,133 g, 0,20 mmol) fue disuelto en acetona al 20% AQ (2.0 mL) y tratados con piridina (5,0 equivalente 1,0 mmol, 0.8 mL). La reacción fue calentada por irradiación de microondas a 120 ° C durante 10 minutos. A continuación, la mezcla de reacción se enfría a 0 ° C y tratada con CH2Cl2 (1,0 mL). Se ha eliminado la capa acuosa de la reacción. Entonces la reacción se agregó DBU (10 equiv, 0,3 mL, 1,9 mmol) y 2,2,2-trichloroacetonitrile (50 equiv, 1,0 mL, 10 mmol). 15 se le permitió la reacción caliente a rt. Después de la consumición completa del material de partida, la mezcla fue concentrado en vacío. El petróleo crudo se purificó mediante cromatografía flash (10:3 - 1:1 hexanes / EtOAc) darle un 5:1 (gluco-/ manno-) mezcla de productos imidate alfa 3 (0,133 g, 0,174 mmol, 87% en conjunto). Bajo estas condiciones de reacción manno-configurar material de partida es más resistente a la hidrólisis como se mencionó anteriormente. En esta reacción, > 95% de gluco-configurar material de partida fue convertido con éxito a alfa imidate 3 mientras que el 62% de la manno-configurado material de partida se convirtió en producto imidate. Datos espectroscópicos de acuerdo con datos previamente registrados21. Como una mezcla de isómeros de C-2 complejo: 1H NMR (400 MHz, CDCl3) δ 8.64 (s, 1 H), 6.46 (d, J = 3,6 Hz, 1 H), 5.54 (m, J = 9,6 Hz), 5.33 (d, J = 3,6 Hz), 5.11 (dd, J = 10,6 Hz, J = 7,9 Hz), 5.04 (dd, J = 9.6, 3,6 Hz), 4,93 (dd, J = 10.6, 3,6 Hz, 1 H), 4.49 (d, J = 7,9 Hz, 1 H), 4.48 (m, 1 H) 4.10 (m, 4 H), 3,85 (m, 2 H), 2.14 (s, 3 H), 2.09 (s, 3 H,), 2.06 (s, 3 H), 2.02 (s, 6 H), 1.99 (s, 3 H), 1.95 (s, 3 H); 13 C RMN (100 MHz, CDCl3) δ 171.2, 170.4, 170.2, 170.1, 169,4, 169.2, 169.0, 162,1, 101.3, 92.9, 76,6, 71.2, 70.9, 70,8, 69,8, 69.5, 69.2, 66.7, 61.5, 60.8, 21.1, 21.0, 20.7, 20.6.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56610/56610fig3v3.jpg"> Figura 3. Ejemplo de hidrólisis (4 ->5) y la conversión de un pote de ester 2-azido-1-nitrato de 4 (4->6). <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig3v3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
((acetato de 3aR,4R,7R,7aR)-7-azido-6-hydroxy-2,2-dimethyltetrahydro-4H-[1,3]dioxolo[4,5-c]pyran-4-yl)methyl (6). Azidonitrate ester 4 (1,0 equiv, 0,150 g, 0.451 mmol) en una solución de 1:4 (4,0 mL) de agua/acetona y piridina (5,0 equivalente, 0,18 mL, 2.26 mmol) fue calentado por irradiación de microondas a 110 ° C durante 10 minutos. Entonces, la reacción fue vial se concentró en una corriente de aire para reducir la mezcla solvente a ~1/2 su volumen inicial. La mezcla de crudo de reacción se agregó CH2Cl2 (4,0 mL). Se ha eliminado la capa acuosa de la reacción. La reacción se adicionaron DBU (2,0 equiv, 0,14 mL, 0.90 mmol) y 2,2,2-trichloroacetonitrile (10 equiv, 0,45 mL, 4,51 mmol) a 0 ° C. En 30 minutos, la reacción se concentró a un crudo marrón oscuro. El petróleo crudo se pasa a través de un tapón de gel de sílice en un embudo de filtro concentrado y purificado mediante cromatografía flash (2:5 EtOAc/hexanes) darle un imidate de 34: 1 mezcla (alfa/beta) 6 (0,189 g, 0.438 mmol, > 95%) como un aceite amarillo. Datos espectroscópicos de acuerdo con datos previamente registrados21. Rƒ 0.26 (1:3 EtOAc/hexanes); [Α] D20 ° +6,63 (c 0.3, CHCl3); IR (película delgada, cm-1) 3943.02, 3689.98, 3053.89, 2986.53, 2684.50, 2409.92, 2304.81, 2115.20, 1735.63, 1674.77, 1616.82, 1421.56, 1265.14, 741.47, 705.37; 1H NMR (400 MHz, CDCl3): anomer alfa δ8.75 (s, 1 H), 6.34 (d, J = 3,4 Hz, 1 H), 4.48 (dd, 1 H, J = 5.5, 7,9 Hz, 1 H), 4,44-4.24 (m, 4 H) 3,76 (dd, J = 3.4, 7,7 Hz, 1 H), 2.04 (s, 3 H), 1,54 (s, 3 H), 1,36 (s, 3 H); 13C (100 MHz, CDCl3): δ170.69, 160.47 110.54, 94.34, 90.67, 73.35, 72.32, 68.13, 63.13, 60.11, 27.92, 26.00, 20,75; HRQ-TOF/MS (m/z): importe anual calculado para [M+Na]+, C13H17Cl3N4O6, 453.0111, encontrar 453.1277.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56610/56610fig4v3.jpg"> Figura 4. Ejemplo de hidrólisis (7 ->8) y la conversión de un pote de ester 2-azido-1-nitrato de 7 (7->9). <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig4v3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
Diacetato de 2R,3S,4R,5R,6R)-2-(acetoxymethyl)-5-azido-6-(2,2,2-trichloro-1-iminoethoxy)tetrahydro-2H-pyran-3,4-diyl y (2R,3S,4R,5S,6R)-2-(acetoxymethyl)-5-azido-6-(2,2,2-trichloro-1-iminoethoxy)tetrahydro-2H-pyran-3,4-diyl Diacetato de (9). Un 1:14.4:27.4 (beta gluco- / alfa manno- / alfa gluco-) mezcla de triacetato 7 (1,0 equiv, 0,438 g, 1.164 mmol) en una solución de 1:4 (10,0 mL) de agua/acetona y piridina (5,0 equivalente, 0,47 mL, 5,82 mmol) fue calentado por irradiación de microondas a 120 ° C por 20 min. Luego, el frasco de reacción se concentró en una corriente de aire para reducir la cantidad inicial de solvente mezcla a ~1/2 de su volumen inicial. La mezcla de crudo de reacción se agregó CH2Cl2 (10,0 mL). Se ha eliminado la capa acuosa de la reacción. La reacción se adicionaron DBU (1,0 equiv, 0,18 mL, 1.164 mmol) y 2,2,2-trichloroacetonitrile (10 equiv, 1,2 mL, 11.64 mmol) a 0 ° C. En 1 h, la reacción fue una luz naranja y el pH de la reacción de mezcla fue de 7. Adicional DBU (1,0 equiv, 0,18 mL, 1.164 mmol) fue agregado y la reacción rápidamente volvió a su característico color marrón oscuro. A las 3 h, la reacción se concentró a crudo marrón oscuro. El petróleo crudo se purificó mediante cromatografía flash (2:5 EtOAc/hexanes) para dar un 1:1.7 gluco- / manno - configurado mezcla de imidate alfa 9 (0,3758 g, 0.790 mmol, 68%) como un aceite amarillo. Datos espectroscópicos de acuerdo con datos previamente registrados21. 1 H RMN (400 MHz, CDCl3): como una mezcla compleja de isómeros: δ 8.68 (s), 6,51 (d, J = 3.7 Hz), 5.51 (m), 5.13 (m), 5.09 (dd, J = 10.3, 3.7 Hz), 4.24 (dd, J = 12.0, Hz 3,8), 4.19-4.15 (m) 4.09 (dd, J = 12.0, 1,8 Hz), 2.02 (s) , 2.00 (s), 1.98 (s), 1.97 (s); 13 C RMN (100 MHz, CDCl3): δ 170.5, 170.0, 169.8, 169.5, 160.7, 92.9, 90.7, 70.0, 69,8, 69.7, 67.7, 61.4, 20.7, 20.6, 20.5.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56610/56610fig5.jpg"> Figura 5. 1 Espectros de H y 13C 3. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig5large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56610/56610fig6.jpg"> Figura 6. 1 Espectros de H y 13C 6. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig6large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/56610/56610fig7.jpg"> Figura 7. 1 H y 13C espectros de 9. <a href="//cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56610/56610fig7large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>

Watch this Scientific Journal Video about One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates at JoVE.com

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

One-pot asistida por microondas conversión de ésteres de nitrato anomérico en Trichloroacetimidates

Un 2-azido-1-nitrato-éster se puede convertir en el correspondiente 2-azido-1-trichloroacetimidate en un procedimiento one-pot. El objetivo del manuscrito es demostrar la utilidad del reactor de microondas en la síntesis de hidratos de carbono.

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate ...

one-pot-microwave-assisted-conversion-anomeric-nitrate-esters-to

Nanyang Technological University

Research

JoVE Journal

Chemistry

7.4K vistas.  Vanderbilt University. Un 2-azido-1-nitrato-éster se puede convertir en el correspondiente 2-azido-1-trichloroacetimidate en un procedimiento one-pot. El objetivo del manuscrito es demostrar la utilidad del reactor de microondas en la síntesis de hidratos de carbono.

Video: One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

Asistida por microondas intramoleculares Dehydrogenative Diels-Alder para la síntesis de naftalenos funcionalizados / Tintes solvatocrómico

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Investigación

Química

Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large variety of PEG molecular weights and configurations (arm number, arm length, and branching pattern) affords researchers tight control over resulting hydrogel structures and properties, including Young&#8217;s modulus and mesh size. This video will illustrate a rapid, efficient, solvent-free, microwave-assisted method to methacrylate PEG precursors into poly(ethylene glycol) dimethacrylate (PEGDM). This synthetic method provides much-needed starting materials for applications in drug delivery and regenerative medicine. The demonstrated method is superior to traditional methacrylation methods as it is significantly faster and simpler, as well as more economical and environmentally friendly, using smaller amounts of reagents and solvents. We will also demonstrate an adaptation of this technique for on-resin methacrylamide functionalization of peptides. This on-resin method allows the N-terminus of peptides to be functionalized with methacrylamide groups prior to deprotection and cleavage from resin. This allows for selective addition of methacrylamide groups to the N-termini of the peptides while amino acids with reactive side groups (e.g.&#160;primary amine of lysine, primary alcohol of serine, secondary alcohols of threonine, and phenol of tyrosine) remain protected, preventing functionalization at multiple sites. This article will detail common analytical methods (proton Nuclear Magnetic Resonance spectroscopy (;H-NMR) and Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-ToF)) to assess the efficiency of the functionalizations. Common pitfalls and suggested troubleshooting methods will be addressed, as will modifications of the technique which can be used to further tune macromer functionality and resulting hydrogel physical and chemical properties. Use of synthesized products for the formation of hydrogels for drug delivery and cell-material interaction studies will be demonstrated, with particular attention paid to modifying hydrogel composition to affect mesh size, controlling hydrogel stiffness and drug release.

Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

This video will illustrate a rapid, efficient method to methacrylate poly(ethylene glycol), enabling chain polymerizations and hydrogel synthesis. It will demonstrate how to similarly introduce methacrylamide functionalities into peptides, detail common analytical methods to assess functionalization efficiency, provide suggestions for troubleshooting and advanced modifications, and demonstrate typical hydrogel characterization techniques.

Funcionalización asistida por microondas de poli (etilenglicol) y los péptidos sobre resina para uso en polimerizaciones de cadena y Formación de hidrogel

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large ...

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile N-(2-alkoxyvinyl)sulfonamides, which react under a variety of conditions to afford useful N- and O-containing compounds. Acid-catalyzed addition of alcohols or thiols to N-(2-alkoxyvinyl)sulfonamide-containing phthalans provides access to ketals and thioketals, respectively. Selective reduction of the vinyl group in N-(2-alkoxyvinyl)sulfonamide-containing phthalans via hydrogenation yields the corresponding phthalan in good yield, whereas reduction with sodium bis(2-methoxyethoxy)aluminumhydride generates a ring-opened phenethylamine analogue. Because the N-(2-alkoxyvinyl)sulfonamide functional group is synthetically versatile, but often hydrolytically unstable, this protocol emphasizes key techniques in preparing, handling, and reacting these pivotal substrates in several useful transformations.

Preparation of N-2-alkoxyvinylsulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Representative experimental procedures for the synthesis of N-(2-alkoxyvinyl)sulfonamides and subsequent conversion to phthalan and phenethylamine derivatives are presented in detail.

Preparación de N-(2-alkoxyvinyl) sulfonamidas de N- tosyl-1,2,3-triazoles y posterior conversión a Phthalans sustituidos y fenetilaminas

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile ...

Reducing Willow Wood Fuel Emission by Low Temperature Microwave Assisted Hydrothermal Carbonization

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative environmental impact and slag formation. The selected short rotation coppice (SRC) willow wood has a high ash content (<img alt="Equation 1" src="/files/ftp_upload/58970/58970eq1.jpg" /> = 1.96%) and, therefore, a high content of emission and slag precursors. Therefore, the reduction of minerals from SRC willow wood by low temperature microwave assisted hydrothermal carbonization (MAHC) at 150 &#176;C, 170 &#176;C, and 185 &#176;C is investigated. An advantage of MAHC over conventional reactors is an even temperature conductance in the reaction medium, as microwaves penetrate the whole reactor volume. This allows a better temperature control and a faster cooldown. Therefore, a succession of depolymerization, transformation and repolymerization reactions can be analyzed effectively. In this study, the analysis of the mass loss, ash content and composition, heating values and molar O/C and H/C ratios of the treated and untreated SCR willow wood showed that the mineral content of the MAHC coal was reduced and the heating value increased. The process water showed a decreasing pH and contained furfural and 5-methylfurfural. A process temperature of 170 &#176;C showed the best combination of energy input and ash component reduction. The MAHC allows a better understanding of the hydrothermal carbonization process, while a large-scale industrial application is unlikely because of the high investment costs.

A protocol for the emission precursor depletion from low quality biomass by low temperature microwave assisted hydrothermal carbonization treatment is presented. This protocol includes the microwave parameters and the analysis of the biocoal product and process water.

Reduciendo la emisión de combustible de madera de sauce por microondas de baja temperatura asistida por carbonización hidrotérmica

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative ...

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 clusters have been observed as intermediates in the synthesis of InP quantum dots from molecular precursors (In(O2CR)3, HO2CR, and P(SiMe3)3) and may be isolated as a pure reagent for subsequent study and use as a single-source precursor. These clusters readily convert to crystalline and relatively monodisperse samples of quasi-spherical InP quantum dots when subjected to thermolysis conditions in the absence of additional precursors above 200 &#176;C. The optical properties, morphology, and structure of both the clusters and quantum dots are confirmed using UV-Vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The molecular symmetry of the clusters is additionally confirmed by solution-phase 31P NMR spectroscopy. This protocol demonstrates the preparation and isolation of atomically-precise InP clusters, and their reliable and scalable conversion to InP QDs.

Synthesis of In37P20O2CR51 Clusters and Their Conversion to InP Quantum Dots

A protocol for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots is presented.

Síntesis de37P20(O2CR)51 racimos y su conversión a puntos cuánticos INP

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 ...

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

A synthetic process for the preparation of a variety of 1-aryl-1H-pyrazole-5-amines was developed. The microwave-mediated nature of this method makes it efficient in both time and resources and utilizes water as the solvent. 3-Aminocrotononitrile or an appropriate &#945;-cyanoketone is combined with an aryl hydrazine and dissolved in 1 M HCl. The mixture is then heated in a microwave reactor at 150 &#176;C, typically for 10-15 min. The product can be readily obtained by basifying the solution with 10% NaOH and isolating the desired compound with a simple vacuum filtration. The use of water as a solvent in this reaction lends to its ease and utility in production, and this method is easily reproducible with a variety of functional groups. Typical isolated yields range from 70-90%, and reactions can be performed on the milligram to gram scale with little to no change in observed yields. Some of the applications of these molecules and their derivatives include pesticides, anti-malarials, and chemotherapeutics, among many others.

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

1-Aryl-1H-pyrazole-5-amines are prepared from aryl hydrazines combined with either 3-aminocrotononitrile or an &#945;-cyanoketone in a 1 M HCl solution using a microwave reactor. Most reactions are done in 10-15 minutes and pure product can be obtained via vacuum filtration with typical isolated yields of 70-90%.

Preparación asistida por microondas de 1-Aryl-1H-pyrazole-5-amines

A synthetic process for the preparation of a variety of 1-aryl-1H-pyrazole-5-amines was developed. The microwave-mediated nature of this method makes it ...

Hierarchical and Programmable One-Pot Oligosaccharide Synthesis

This article presents a general experimental protocol for programmable one-pot oligosaccharide synthesis and demonstrates how to use Auto-CHO software for generating potential synthetic solutions. The programmable one-pot oligosaccharide synthesis approach is designed to empower fast oligosaccharide synthesis of large amounts using thioglycoside building blocks (BBLs) with the appropriate sequential order of relative reactivity values (RRVs). Auto-CHO is a cross-platform software with a graphical user interface that provides possible synthetic solutions for programmable one-pot oligosaccharide synthesis by searching a BBL library (containing about 150 validated and &#62;50,000 virtual BBLs) with accurately predicted RRVs by support vector regression. The algorithm for hierarchical one-pot synthesis has been implemented in Auto-CHO and uses fragments generated by one-pot reactions as new BBLs. In addition, Auto-CHO allows users to give feedback for virtual BBLs to keep valuable ones for further use. One-pot synthesis of stage-specific embryonic antigen 4 (SSEA-4), which is a pluripotent human embryonic stem cell marker, is demonstrated in this work.

This protocol demonstrates how to use the Auto-CHO software for hierarchical and programmable one-pot synthesis of oligosaccharides. It also describes the general procedure for RRV determination&#160;experiments and one-pot glycosylation of SSEA-4.

Síntesis jerárquica y programable de oligosacáridos de una olla

This article presents a general experimental protocol for programmable one-pot oligosaccharide synthesis and demonstrates how to use Auto-CHO software for ...

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products and notably to generate chiral carbon centers. The crucial first step consists in the selective double hydroboration of CO2 catalyzed by an iron hydride complex. The product obtained with this 4 e- reduction is a rare bis(boryl)acetal, compound 1, which is subjected in situ to three different reactions in a second step. The first reaction concerns a condensation reaction with (diisopropyl)phenylamine affording the corresponding imine 2. In the second and third reaction, intermediate 1 reacts with triazol-5-ylidene (Enders&#39; carbene) to afford compounds 3 or 4, depending on the reaction conditions. In both compounds, C-C bonds are formed, and chiral centers are generated from CO2 as the only source of carbon. Compound 4 exhibits two chiral centers obtained in a diastereoselective manner in a formose-type mechanism. We proved that the remaining boryl fragment plays a key role in this unprecedented stereocontrol. The interest of the method stands on the reactive and versatile nature of 1, giving rise to various complex molecules from a single intermediate. The complexity of a two-step method is compensated by the overall short reaction time (2 h for the larger reaction time), and mild reaction conditions (25 &#176;C to 80 &#176;C and 1 to 3 atm of CO2).

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations are conducted in a one-pot two-step procedure for the synthesis of complex molecules. The selective 4 e- reduction of CO2 with a hydroborane reductant affords a reactive and versatile bis(boryl)acetal intermediate which is subsequently involved in condensation reaction or carbene-mediated C-C coupling generation.

Transformaciones versátiles de CO2 en productos complejos: una estrategia de dos pasos de un solo precio

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products ...

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal catalysis, the literature on direct heteroarylation is scarce. The presence of heteroatoms such as nitrogen, sulfur and oxygen often make heteroarylation a challenging research field due to catalyst poisoning, product decomposition and the rest. This protocol details a highly efficient direct &#945;-C(sp3) heteroarylation of ketones under microwave irradiation. Key factors for successful heteroarylation include the use of XPhos Palladacycle Gen. 4 Catalyst, excess base to suppress side reactions and the high temperature and pressure achieved in a sealed reaction vial under microwave irradiation. The heteroarylation compounds prepared by this method were fully characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and high-resolution mass spectrometry (HRMS). This methodology has several advantages over literature precedents including broad substrate scope, rapid reaction time, greener procedure and operational simplicity by eliminating the preparation of intermediates such as silyl enol ether. Possible applications for this protocol include, but are not limited to, diversity-oriented synthesis for the discovery of biologically active small molecules, domino synthesis for the preparation of natural products and ligand development for new transition metal catalytic systems.

Heteroaryl compounds are important molecules utilized in organic synthesis, medicinal and biological chemistry. A microwave-assisted heteroarylation using palladium catalysis provides a rapid and efficient method to attach heteroaryl moieties directly to ketone substrates.

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Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal ...

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