32. “A Novel Cycloaddition Reaction of Thermally Generated Sulfenes”
    U. Burger, S.P. Schmidlin, J. Mareda, G. Bernardinelli
    CHIMIA 1992, 46, 111-113.

The highly strained γ-sultine 4, resulting from the addition of SO₂ to benzobenzvalene, is shown to undergo a thermal cycloreversion which gives 1H-indene-1-thiocarbaldehyde dioxide (6) as an intermediate and subsequently 1H-indene-1-carbaldehyde (5). The sulfene can be intercepted with electron poor C=C bonds in a cycloaddition process leading to a five-membered ring. The structure of the fused heterocyclic product 8b resulting from addition of the sulfene 6 to N-phenyl-maleimide was ascertained by X-ray analysis. Pent-4-enethial dioxide (12) produced by a sulfo-Cope rearrangement from allyl vinyl sulfone (11) is found to add to N-phenylmaleimide in the same 1,3-dipolar fashion as the sulfene 6. The cycloadditions need not be via concerted pathways.

Lien : http://www.ingentaconnect.com/content/scs/chimia/1992/00000046/00000004/art00008 

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