A three-component reaction of cyclobutanone oxime esters, sulfur dioxide and -alkyl--methacryloyl benzamides.

A three-component reaction of cyclobutanone oxime esters, DABCO·(SO) and -alkyl--methacryloyl benzamides is described. This reaction proceeds without the addition of any oxidant or transition metal, affording sulfonyl-containing isoquinoline-1,3-(2,4)-diones in moderate to good yields. Various functional groups are tolerated well in this transformation. Mechanistic studies suggest that a radical pathway is involved, including β-scission, sulfur dioxide insertion, and intramolecular cyclization processes.