Methyl dithiocrotonate

The reaction of methyl dithiocrotonate with cyclopentadiene was shown to provide the cycloadduct 13. The initial assumption that the product was derived from dithioester 2ir participation in an all-carbon Diels-Alder reaction with cyclopentadiene followed by a PPJ-sigmatro pic rearrangement was shown not to be operative. Consequently, the generation of 13 resulted from the direct 4ir participation of the a,/3-unsaturated dithioester in a Diels-Alder reaction with cyclopentadiene [Eq. (8)]. ... 

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