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(sp 3 ) quaternary center were obtained in good to high yields. InCl 3 -catalyzed cascade cyclization of allenyl-enal and aniline gave a valuable pyrrolo[1,2- a ]quinoline motif.