Transition-Metal-Free Cross-Coupling Reaction of Iodocarboranes with Terminal Alkynes Enabled by UV Light: Synthesis of 1-Alkynyl--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--carboranes. Moreover, following this strategy, the introduction of 1-I-3-aryl--carboranes or 1-I-2-aryl--carboranes results in the formation of -carborane-fused cyclics. Interestingly, when 1-I-3-(-R-CH)--carboranes are chosen as coupling partners, unexpected R-group 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.