Reaction of o-Carboryne with Furans: Facile Synthesis of Carborane-Fused Oxanorbornenes and Their Derivatives

o-Carboryne (1,2-dehydro-o-carborane) is a very useful synthon for the synthesis of a variety of carborane-functionalized molecules. Diels-Alder reaction of o-carboryne with furans gave a series of carborane-fused oxanorbornenes in moderate to high yields using 1-OTf-1,2-C2B10H11 as carboryne precursor. The resultant cycloadducts can undergo hydrogenation, cyclic oxidation, bromination, [4+2]/[2+2] cycloaddition and nucleophilic ring opening reaction to afford a variety of highly functionalized carboranes that may find applications as useful basic units in medicine and materials science.