Generation and reactivity of o-carborynes

Abstract

o-Carboryne (1,2-dehydro-o-carborane) is a very reactive intermediate that can be generated in situ from 1-Br-2-Li-1,2-C₂B₁₀H₁₀, 1-I-2-Li-1,2-C₂B₁₀H₁₀ or 1-Me₃Si-2-[IPh(OAc)]-1,2-C₂B₁₀H₁₀. It exists in two resonance forms, a bonding form vs. a biradical form. Each form demonstrates unique reactivity patterns. o-Carboryne can undergo various types of reactions such as [4 + 2]/[2 + 2] cycloaddition, ene reaction, hydrogen abstraction, and sp²/sp³ C–H bond insertion reaction with a broad spectrum of substrates including alkenes, alkynes, (hetero)aromatics, ethers, and ferrocenes. It is a very useful synthon for generating a variety of functionalized carboranes that have potential applications in medicine, materials science and organometallic/coordination chemistry. This perspective offers an overview of recent advances in this interesting research field.