Transition-metal-free cross-coupling reaction of iodocarboranes with terminal alkynes enabled by UV light : Synthesis of 1-alkynyl-o-carboranes and carborane-fused cyclics

A transition-metal-free coupling protocol between iodocarboranes and terminal alkynes enabled by light at room temperature has been developed, leading to the synthesis of a variety of 1-alkynyl-o-carboranes. Moreover, following this strategy, the introduction of 1-I-3-aryl-o-carboranes or 1-I-2-aryl-o-carboranes results in the formation of o-carborane-fused cyclics. Interestingly, when 1-I-3- (p-R-C₆H₄)-o-carboranes are chosen as coupling partners, unexpected Rgroup migration products are also isolated. On the basis of the results of control experiments and isolation of the key intermediates, a possible reaction mechanism is then proposed, involving the formation of spiro radical species.