Reaction of carboryne with alkylbenzenes

Carboryne (1,2-dehydro-o-carborane), in situ generated from the precursor 1-iodo-2-lithiocarborane, reacted with alkylbenzenes to give two regioisomers of the [4 + 2] cycloadducts as the major products in moderate to good yields, in which the steric factors play an important role in the regioselectivity. Minor products derived from benzylic C-H insertion reaction, annulation reaction, tandem [4 + 2] cycloaddition/homo Diels-Alder reaction, and tandem ene reaction/[2 + 2] cycloaddition were also isolated and characterized in the reaction of carboryne with toluene. The presence of AgF in the above reaction produced no notable changes in the product distributions and yields.