Consecutive intermolecular 1,1-carboboration reactions of Me3Si-substituted alkynes with the halogeno-B(C6F5)2 reagents

Abstract

1-(Trimethylsilyl)propyne 2a reacts with halogenoboranes XB(C₆F₅)₂ (X: Cl, Br) in a 1 : 1 molar ratio at r.t. to give the respective alkenylboranes 3. These undergo a subsequent 1,1-alkenylboration reaction with additional alkyne 2a to give the persubstituted 3-boryl-2,4-hexadiene products 4. The conjugated diyne bis(trimethylsilyl)butadiyne 2d reacts with ClB(C₆F₅)₂ in a 2 : 1 molar ratio by a sequence of consecutive 1,1-carboboration reactions to give the persubstituted borylated octadiendiyne product 6.