Synthesis of Polyhedral Borane Cluster Fused Heterocycles via Transition Metal Catalyzed B-H Activation.

Ke Cao,Mao Chen,Ji Wu,Junxiao Yang,Wen-Jun Jiang,Tao-Tao Xu,Xin-Yu Wen,Cai-Yan Zhang

doi:10.3390/molecules25020391

Ke Cao, Mao Chen + Show 6 more

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https://doi.org/10.3390/molecules25020391

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Abstract

Aromatic heterocycles are ubiquitous building blocks in bioactive natural products, pharmaceutical and agrochemical industries. Accordingly, the carborane-fused heterocycles would be potential candidates in drug discovery, nanomaterials, metallacarboranes, as well as photoluminescent materials. In recent years, the transition metal catalyzed B-H activation has been proved to be an effective protocol for selective functionalization of B-H bond of o-carboranes, which has been further extended for the synthesis of polyhedral borane cluster-fused heterocycles via cascade B-H functionalization/annulation process. This article summarizes the recent progress in construction of polyhedral borane cluster-fused heterocycles via B-H activation.

Highlights

Icosahedral carboranes are a class of carbon-boron molecular clusters with three dimensional aromaticity analogues to benzene, the features of high boron content, extraordinary thermal and chemical stability, and synthetic flexibility make the carborane derivatives be a kind of important building blocks in functional materials [1,2,3,4], key frameworks in pharmaceuticals [5,6,7,8] and ligands in organometallic chemistry [9,10,11,12,13]
Based on the directing group guided/transition metal-catalyzed B-H activation for selective functionalization of o-carboranes, the copper catalyzed [4+2] annulation of carboranyl amides with internal alkynes for synthesis of o-carborane-fused pyridones were accomplished under the assistance of 8-aminoquinoline (Figure 2) [48]
The transition metal-catalyzed B-H activation as a novel synthetic strategy has been proved to be an effective protocol for selective functionalization of B-H bond of polyhedral borane clusters, which has been further extended to synthesis of polyhedral borane cluster-fused heterocycles via cascade B-H

Summary

Introduction

Icosahedral carboranes are a class of carbon-boron molecular clusters with three dimensional aromaticity analogues to benzene, the features of high boron content, extraordinary thermal and chemical stability, and synthetic flexibility make the carborane derivatives be a kind of important building blocks in functional materials [1,2,3,4], key frameworks in pharmaceuticals [5,6,7,8] and ligands in organometallic chemistry [9,10,11,12,13]. In recent years, inspired by the C-H activation for direct functionalization of carbon-based molecules, the transition metal-catalyzed B-H activation has emerged as a powerful strategy for selective functionalization of o-carboranes and resulted in much advancement [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40].

Synthesis of o-Carborane-Fused Heterocycles

Synthesis of nido-Carborane-Fused Heterocycles

Conclusions