Photocatalytic Carbosulfonylation/Cyclization of <i>N</i>-Homoallyl and <i>N</i>-Allyl Aldehyde Hydrazones toward Sulfonylated Tetrahydropyridazines and Dihydropyrazoles

Abstract

N ′-Benzylidene- N -homoallylacetohydrazides were designed and synthesized as novel skeletons for the construction of functionalized tetrahydropyridazines. A series of aryl- and alkylsulfonylated tetrahydropyridazines were obtained in yields of up to 94% employing sulfonyl chlorides as the sulfonyl radical sources under visible-light irradiation. Besides, sulfonylated dihydropyrazoles were also produced from N -allyl- N ′-benzylideneacetohydrazides. Mechanistic investigations indicated that both energy transfer and single electron transfer processes were involved in accomplishing the radical 6/5- endo - trig cyclization to the C═N bond.

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