Directing-Group-Assisted Transition-Metal-Catalyzed Selective BH Functionalization of o-Carboranes

Abstract Carboranes are a type of molecular clusters consisting of carbon, hydrogen, and boron atoms. They possess unique characteristics, such as three-dimensional aromaticity, icosahedral geometry, and robustness. Functionalized carboranes have been utilized in various fields, including medicine, materials, and organometallic/coordination chemistry. In this context, selective functionalization of o-carboranes has received tremendous attention, specifically in the regio- and enantioselective modification of the ten chemically similar BH vertices within the carborane cage. In recent years, significant progress has been made in catalytic vertex-specific BH functionalization, as well as achieving enantioselective functionalization of the cage BH. This review provides an overview of the recent advancements in this research field. 1 Introduction 2 Carboxy-Assisted BH Functionalization 2.1 Formation of B–C Bonds 2.2 Formation of B–N Bonds 2.3 Formation of B–O Bonds 2.4 Formation of B–X Bonds 2.5 Consecutive Formation of B–C and B–Y (Y = N, O) Bonds 3 N-Based Directing-Group-Assisted B–H Functionalization 3.1 Acylamino as a Directing Group 3.2 Amide as a Directing Group 3.3 Pyridyl as a Directing Group 3.4 Imine as a Directing Group 4 Phosphinyl-Assisted Cage B–H Functionalization 5 Bidentate-Directing-Group-Assisted B–H Functionalization 6 Other Directing-Group-Assisted B–H Functionalization 7 Conclusions