A7-Mesembrenone

A tandem sulfide-contraction and Robinson annelation reaction51 was used for the synthesis of a me-sembrine analog, A7-mesembrenone (133). The aryl-substituted thiobutyrolactam (130) was treated with chloromethyl vinyl ketone followed by diisopropylethylamine to afford A7-mesembrenone (133) in good yield (Scheme 29). The reaction probably proceeds through initial sulfide contraction to the intermediate vinyl enaminone (131), which tautomerized to the enamine (132) and underwent intramolecular Michael closure to produce (133). 

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