Direct transformation of Baylis-Hillman acetates into N-substituted quinolones through an ^SN²â€²â†’ ^SNAr→(Δ^3,4-Δ^2,3 shift)→oxidation sequence

When subjected to tandem SN2-SNAr cyclization in the presence of alkyl or aralkyl amines, Baylis-Hillman acetates gave the corresponding 1,2-dihydroquinolines, which on simple exposure to light and oxygen afforded the corresponding 4- and 2-quinolones through sensitized oxidation or a 3,4-2,3 shift oxidation cascade. The mechanism of the oxidation step, the stabilities of the 1,2- and 1,4-dihydroquinolines in solution and in the solid state, and the synthetic elaboration of the key intermediates to known therapeutic agents are discussed. © Georg Thieme Verlag Stuttgart · New York.