Silylium ion-mediated cage-opening functionalization of closo-B10H102− salts

Abstract

The cage-opening functionalization of stable closo-B₁₀H₁₀²⁻ salts is a great way to get various boron clusters. However, the known methods to mediate cage-opening functionalization rely on the use of strong acids, which suffer from low efficiency and narrow substrate scope. Herein, an efficient method to synthesize 6-substituted decaboranyl ethers and sulfides has been developed. The reaction was mediated by trimethylsilyl trifluoromethanesulfonate (TMSOTf) and occurred at room temperature. Six 6-substituted ethers were obtained in 65–92% yields and five 6-substituted sulfides were prepared in 38–58% yields. The reaction had excellent regioselectivity, affording the single B(6) regioisomer in all cases. The interaction between the B–H bonds of the boron cage and the silylium ion was believed to be the key factor in the reaction.