Regiodivergent synthesis of vinyl trifluoromethansulfonates γ/δ lactones: Via 1,6 addition/intramolecular one-pot annulation of 1,4-dihidropyridines derivated from pyridinyl propenones

We report a novel intramolecular 1,6 oxa-Michael addition on substituted dihydropyridines to obtain 5 and 6 member ring lactones in an one-pot reaction starting from activated pyridinyl propenones, without organic catalysis or presence of bulky groups in the Michael acceptor. A marked dependence on the regioselectivity of ring closure was found, dependent on the propenone used.