Metal-Free 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-Mediated Cross-Dehydrogenative-Coupling (CDC) of Benzylic C(sp3)-H Bonds and Vinylic C(sp2)-H Bonds: Efficient One-Pot Synthesis of 1H-Indenes

A novel 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-promoted intermolecular crossdehydrogenative coupling reaction of alkyl C(sp(3))-H bonds not adjacent to heteroatoms with vinylic C(sp(2))-H bonds has been developed. This new strategy provides a new, environmentally friendly, and efficient protocol for the synthesis of polysubstituted 1H-indenes in a single step via a radical-initiated two C(sp(2))-C(sp(2)) and C(sp(2))-C(sp(3)) bond formation process.