Ene Reaction of o-Carboryne with Alkynes and Alkenes at Room Temperature: Synthesis of o-Carboranyl Allenes and Alkenes

o-Carboryne undergoes at room temperature an efficient ene reaction with a large variety of alkynes and alkenes possessing an α-CH proton to give a series of o-carboranyl allenes and alkenes in good to high isolated yields. This reaction has a broad substrate scope from alkyl and aryl to silyl substituents. This protocol provides a facile synthetic method for accessing cage C-substituted carboranyl allenes and alkenes, which may be utilized as useful starting materials to synthesize multifunctionalized carboranes.