Organosuperbase Catalyzed 1,1-Diboration of Alkynes

Abstract

1,1-diboryl alkenes are versatile building blocks in organic synthesis and medicinal chemistry. There have been only a small number of established methods to prepare this class of compounds and most of them used transition metal catalysts, which are undesirable in the preparation of bioactive compounds. Herein, we report an unprecedented application of P1-tBu as an organocatalyst to promote 1,1-diboration reactions of unactivated aromatic as well as electron-deficient terminal alkynes. The strong basicity of this phosphazene enables the activation of reaction substrates while its steric bulk allows for high regio- and stereo-selectivity to be obtained. A combination of experimental and computational studies suggests interesting mechanistic insights for these phosphazene-catalyzed diboration reaction, which are also discussed in detail.