The addition of methylborylene to acetylenes: Synthesis of 1,4-diboracyclohexa-2,5-dienes, and of a borirene and a diboretene derivative

The synthesis of 1,4-dimethyl-2,3,5,6-tetra- n-alkyl-1,4-diboracyclohexa-2,5-dienes from the reaction of di- n-alkylacetylenes with the methylborylene-generating system 2C 8K/MeBBr 2 is described. A mechanism for these reactions is proposed. The addition of methylborylene to di- t-butylacetylene results in the formation of 1-methyl-2,3-di- t-butylborirene and of 1,3-dimethyl-2,4-di- t-butyl-1,3-diboretene.