Rhodium-Catalyzed Enal Transfer with N-Methoxypyridazinium Salts

Herein, we report a simple method for functionalized enals involving enal-transfer reaction of water-soluble N-methoxypyridazinium salts. This open-flask reaction proceeds under mild aqueous basic conditions through [2,3]-sigmatropic rearrangement of propargyl/allyl sulfur-ylides derived from in situ-generated Rh-(E)-enalcarbene. Various synthetically challenging allene- and allyl-functionalized (E)-enals with a γ-C(sp3) quaternary center were obtained in good to high yields. InCl3-catalyzed cascade cyclization of allenyl-enal and aniline gave a valuable pyrrolo[1,2-a]quinoline motif.