1,1-Carboboration

The use of very electrophilic boranes RB(C6F5)(2) widens the scope of the 1,1- carboboration reaction substantially. Simple terminal alkynes HC CR 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 RC CR undergo 1,1-carboboration with the RB(C6F5)(2) reagents to provide a novel way of carbon- carbon sigma-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.