Abstract
Reactions of tricarbonyl compounds with vinyl diazo compounds 2 were carried out. Reaction of 1,2,3-indanetrione with 2a, b, c gave the spiroindan-1,3-dione-2,2′-benzodihydrooxepin 7a, b, c , but not normal products oxirane and dihydrofuran derivatives expected from intermediate vinyl carbonyl ylides 4 . Formation of 7 requires isomerization of vinyl carbonyl ylides 4 bearing a ( Z)-cyanostyryl group to unstable ( E)-form 5 and subsequent cyclization to oxepin 6 followed by a 1,5-hydrogen shift. However, reaction of 2 with six-membered cyclic tricarbonyl compounds 1,2,3-trioxo-2,3-dihydrophenalene 11 and dimethylalloxane 13 gave the dioxole 12 and the dihydrofuran 14 , respectively, typical products expected from vinyl carbonyl ylides.
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