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

A three-component reaction of cyclobutanone oxime esters, DABCO·(SO 2 ) 2 and N -alkyl- N -methacryloyl benzamides is described. This reaction proceeds without the addition of any oxidant or transition metal, affording sulfonyl-containing isoquinoline-1,3-(2 H ,4 H )-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.