Nickel Catalyzed Vinylidene Insertions into O-H Bonds.

A (pybox)Ni catalyst (pybox = pyridine-bis(oxazoline)) promotes the reductive cyclization of β-hydroxy 1,1-dichloroalkenes to form 2,3-dihydrofurans. The substrates for this reaction are conveniently prepared by an aldol addition followed by one-carbon homologation. Chiral substrates are accessible in highly enantioenriched form, allowing for the synthesis of stereochemically complex 2,3,4-trisubstituted products. Mechanistic studies support a vinylidene O-H insertion pathway rather than C-O cross-coupling followed by reductive dechlorination.