Synthesis of benzofuranyl indolinones and benzonaphthoxazepinones via reaction of sulfonyl phthalide with nitroisatylidenes

Abstract

Attempted [4+2] Hauser-Kraus annulation of sulfonyl phthalide with nitroisatylidene led to the formation of benzofuranyl indolinones, instead of the expected spironaphthoquinone oxindoles, via nucleophilic vinylic substitution of the nitro group. By contrast, the reaction of sulfonyl phthalide with nitroisoxazolyl isatylidene followed the [4+2] Hauser-Kraus pathway, yielding benzonaphthoxazepinones via spontaneous rearrangement of the initially formed Hauser-Kraus adducts, namely, spironaphthoquinone-oxindoles.