Direct and Regioselective Palladium(II)-Catalyzed B(4)–H Monoacyloxylation and B(4,5)–H Diacetoxylation of o-Carborane Acids with Phenyliodonium Dicarboxylates

Abstract

A direct B(4)–H monoacyloxylation via a Pd-catalyzed regioselective B(4)–H activation of o-carborane acids with phenyliodonium dicarboxylates was developed, and a series of B(4)–H monoacyloxylated o-carboranes decorated with active groups were synthesized with moderate to good yields as well as excellent selectivity. In addition, a direct B­(4,5)–H diacetoxylation from o-carborane acids with phenyliodonium diacetate was demonstrated.

Recent Advance in Transition Metal‐Catalyzed Carboxylic Acid Guided B−H Functionalization of Carboranes

“…The B−O bond formation was also achieved by Lee's group in 2021 (Scheme 30). [39] In the presence of Pd(OAc) 2 catalyst, reaction of carboranyl carboxylic acid with phenyliodonium dicarboxylates gave a series of B(4)−H monoacyloxylated o ‐carboranes with moderate to good yields. In addition, B(4,5)−H diacyloxylated o ‐carboranes were obtained in one pot by this catalytic system.…”

Migration Mechanism of the B−H Activation of Carboranes

“…Although transition metal-mediated regioselective BÀ H activation of carboranes has been reported in recent years, [25][26][27][28][29][30] a transition metal catalysed by BÀ H activation of carboranes to achieve B!B migration is rarely reported. In 1971, Hawthorne and co-authors [31][32] first proposed the concept of metal complex migration on carboranes.…”

Recent Advances in Transition Metal-Catalyzed B—H Bond Activation for Synthesis of o-Carborane Derivatives with B—Heteroatom Bond

“…谢作伟课题组 2016 年报道了羧基导向 的铑催化邻碳硼烷硼-氢键羟基化反应, 该过程可以选 择性地定位于 B(4)-H, 应用氧气同时作为氧化剂和羟 基化试剂, 增强了官能团化过程的经济性和环境友好性 (Scheme 19) [33] . 反应中氧气插入硼-金属键的关键中间 体 Int-20 经由 MALDI-TOF (matrix-assisted laser desorption ionization time-of-flight)高分辨质谱及 18 2021 年 Lee 课题组 [34] 报道了钯催化 1-羧基-邻碳硼…”