anti‐Selective Borylstannylation of Alkynes with (o‐Phenylenediaminato)borylstannanes by a Radical Mechanism

Abstract We have achieved the first anti ‐borylstannylation of alkynes by using ( o ‐phenylenediaminato)borylstannanes. This reaction afforded 1‐boryl‐2‐stannylalkenes with excellent regio‐ and stereoselectivity by a radical mechanism. This anti ‐addition manner is in sharp contrast to the syn ‐selectivity obtained during transition metal‐catalyzed borylstannylation. The mild radical conditions enabled a broad substrate scope, and various types of aromatic and aliphatic alkynes were applicable. The origin of regio‐ and stereoselectivity was elucidated by DFT calculation of the reaction mechanism. The application of the borylstannylation products to cross‐ or homocoupling reactions provided ready access to either triarylethenes or bisborylbutadienes.