One‐Pot Process to Carborano‐Coumarin <i>via</i> Catalytic CascadeDehydrogenative Cross‐Coupling
Yik Ki Au, Hairong Lyu, Yangjian Quan, Zuowei Xie
Abstract
Summary of main observation and conclusion Ir‐catalyzed cascade dehydrogenative CH/BH and BH/OH cross‐coupling of carboranyl carboxylic acid with readily available benzoic acid has been achieved, leading to the facile synthesis of previously unavailable carborano‐coumarin in a simple one‐pot process. Two cage B—H, one aryl C—H and one O—H bonds are activated to construct efficiently new B—C and B—O bonds. The cascade cyclization can stop at the first B—H/C—H cross‐coupling step by tuning the reaction conditions, resulting in a series of α‐carboranyl benzoic acid and aryl carborane derivatives. Control experiments indicate that B—H/C—H dehydrocoupling proceeds preferentially over B—H/O—H dehydrocoupling, and both directing groups and oxidants are crucial for this reaction. An iridium(V) intermediate is proposed to be involved in the catalytic cycle.