Hydrogenation of Borylated Arenes

Abstract

A cis‐selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by rhodium cyclic (alkyl)(amino)carbene (Rh–CAAC) is reported. The reaction tolerates a variety of boron‐protecting groups and provides direct access to a broad scope of saturated, borylated carbo‐ and heterocycles with various functional groups. The transformation is strategically important because the versatile saturated boronate products are difficult to prepare by other methods. The utility of the saturated cyclic building blocks was demonstrated by post‐functionalization of the boron group.

Hydrogenation of (Hetero)aryl Boronate Esters with a Cyclic (Alkyl)(amino)carbene–Rhodium Complex: Direct Access to cis‐Substituted Borylated Cycloalkanes and Saturated Heterocycles

“…In summary, we have developed a selective hydrogenation method to aryl boronate esters by using a CAAC–Rh complex . This process enables the chemo‐ and stereoselective reduction of aromatic compounds, with retention of the valuable boronate functional group, enabling the rapid construction of cis ‐substituted borylated cycloalkanes.…”

“…In summary,wehave developed aselective hydrogenation method to aryl boronate esters by using aC AAC-Rh complex. [23] This process enables the chemo-and stereoselective reduction of aromatic compounds,w ith retention of the valuable boronate functional group,e nabling the rapid construction of cis-substituted borylated cycloalkanes.Multisubstituted aryl boronate esters,n aphthylboronate esters,a s well as nitrogen-and oxygen-containing heteroaryl boronate esters were used as substrates.T his reaction thus constitutes ag eneral strategy for the preparation of otherwise elusive, diversely substituted borylated cycloalkanes and saturated heterocycles that are usually difficult to prepare by conventional methods.F urther studies pertaining to an understanding of the hydrogenation pathway and explorations of synthetic applications are under way.…”

Catalytic Transfer Hydrogenation of Arenes and Heteroarenes

“…Based on our previous experience in selective high‐pressure heterogeneous hydrogenation of fluoro‐, silyl‐, borylated‐arenes and fluoropyridines [24–27] using the Bertrand‐Zeng catalyst, [28, 29] we envisioned that Rh‐CAAC complexes could also be suitable catalyst precursors to develop a transfer hydrogenation reaction for the reduction of benzene derivatives. We began our investigation by assessing the activity of the Bertrand‐Zeng catalyst in transfer hydrogenation reactions using ammonia borane.…”

“…Most notably, this procedure enables the facile reduction of various arenes including valuable silyl‐, trifluoromethyl‐ and borylated‐arenes, which was recently reported using 50 bar of hydrogen gas [25, 26, 33] . To gain a better understanding of the reaction mechanism, different experiments were conducted.…”

Hydrogenation of (Hetero)aryl Boronate Esters with a Cyclic (Alkyl)(amino)carbene–Rhodium Complex: Direct Access to cis‐Substituted Borylated Cycloalkanes and Saturated Heterocycles

“…[23] This process enables the chemo-and stereoselective reduction of aromatic compounds,w ith retention of the valuable boronate functional group,e nabling the rapid construction of cis-substituted borylated cycloalkanes.Multisubstituted aryl boronate esters,n aphthylboronate esters,a s well as nitrogen-and oxygen-containing heteroaryl boronate esters were used as substrates.T his reaction thus constitutes ag eneral strategy for the preparation of otherwise elusive, diversely substituted borylated cycloalkanes and saturated heterocycles that are usually difficult to prepare by conventional methods.F urther studies pertaining to an understanding of the hydrogenation pathway and explorations of synthetic applications are under way. [23] This process enables the chemo-and stereoselective reduction of aromatic compounds,w ith retention of the valuable boronate functional group,e nabling the rapid construction of cis-substituted borylated cycloalkanes.Multisubstituted aryl boronate esters,n aphthylboronate esters,a s well as nitrogen-and oxygen-containing heteroaryl boronate esters were used as substrates.T his reaction thus constitutes ag eneral strategy for the preparation of otherwise elusive, diversely substituted borylated cycloalkanes and saturated heterocycles that are usually difficult to prepare by conventional methods.F urther studies pertaining to an understanding of the hydrogenation pathway and explorations of synthetic applications are under way.…”