1,1-Carboboration

Abstract

The use of very electrophilic boranes RB(C₆F₅)₂ widens the scope of the 1,1-carboboration reaction substantially. Simple terminal alkynes HCCR undergo this reaction with the RB(C₆F₅)₂ reagents rapidly under mild conditions to give high yields of very useful new alkenylborane products. Even internal alkynes RCCR undergo 1,1-carboboration with the RB(C₆F₅)₂ reagents to provide a novel way of carbon–carbon σ-bond activation. Variants of these reactions involving phosphorus substituted alkynes and more complex bisalkynyl main group and transition metal substrates give rise to the formation of very interesting functionalized metallacyclic products upon treatment with RB(C₆F₅)₂ reagents by means of reaction sequences involving selective 1,1-carboboration steps.