Access to Methylidene-Azaspiro[4.5]decatrienones via Radical-Promoted Domino Thio-Functionalization/Dearomative <i>Ipso</i>-Annulation

An unprecedented approach involving radical-mediated sulfonylation/dearomative <i>ipso</i>-annulation of <i>N</i>-(methyl-2-phenylacetate)propiolamides using arylsulfonyl radical, generated from aryl diazonium salt in the presence of DABSO, is developed. This strategy provides uniquely substituted 3-sulfonyl <i>aza</i>spiro[4.5]decatrienones in good yields. The developed approach has also been extended fruitfully to 3-thiocyano <i>aza</i>-spirocycles through domino thiocyanation/dearomative <i>ipso</i>-annulation.