Divinyl sulphone, preparation

The reaction of 2,3-diphenylthiiren 1,1-dioxide (8) with enamines derived from cyclic ketones gives rise to ring-enlargement products such as (9), which contain the divinyl sulphone unit e.g. the reaction of l-(l-cyclohexen-l-yl)-pyrrolidine (10) with the above thiiren gave (9 n = 1), in 86% yield. The ten-and thirteen- to fifteen-membered-ring analogues were also prepared from the... 

A new general and stereospecific synthesis of c/s-l,2-divinyl systems has been achieved by flash vacuum pyrolysis of the 3-thiabicyclo[3.2.0]heptane 3,3-dioxide ring system. For example, the sulphone (61), prepared by photolysis of 2,5-dihydrothiophen 1,1-dioxide and maleic anhydride, eliminates sulphur dioxide to give the 1,5-diene (62) of greater than 99.9 /o c -geometry. 

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