Electro-carbo-cyclization of alkyne-, alkene-, and nitrile-tethered α-halocarbonyls

The electrochemical dehalogenative carbo-cyclization of acyclic precursors provides an efficient method for synthesizing various heterocycles. Typically, C(sp²) aryl radicals undergo intramolecular carbo-cyclization with unsaturated functional groups. In this report, we present, for the first time, a carbo-cyclization involving tertiary C(sp³) radicals reacting with alkynes, alkenes, and nitriles in an undivided cell. This leads to the synthesis of both deuterated and non-deuterated 3,4-dihydroquinolin-2-ones and quinoline-2,4-diones in good yields. The proposed mechanism is supported by the isolation of a 4-benzylidene intermediate.