Deoxygenative Insertion of Carbonyl Carbon into a C(sp³)-H Bond: Synthesis of Indolines and Indoles

A simple deoxygenation reagent prepared in situ from commercially available Mo(CO)₆ and ortho-quinone has been developed for the synthesis of indoline and indole derivatives. The Mo/quinone complex efficiently deoxygenates carbonyl compounds bearing a neighboring dialkylamino group and effects intramolecular cyclizations with the insertion of a deoxygenated carbonyl carbon into a C(sp³)-H bond, in which a carbonyl group acts as a carbene equivalent. The reaction also proceeds with a catalytic amount of Mo/quinone in the presence of disilane as an oxygen atom acceptor.