[3,3]SIGMATROPIC RING EXPANSION OF CYCLIC THIONOCARBONATES .8. HIGHLY STEREOSELECTIVE SYNTHESIS OF (Z)-DOUBLE BONDS OR (E)-DOUBLE BONDS BY CONTROLLING CHAIR-LIKE-BOAT-LIKE TRANSITION-STATES IN THE [3,3]SIGMATROPIC REARRANGEMENT OF 8-MEMBERED THIONOCARBONATES

A highly stereoselective synthesis of (Z)- or (E)-double bonds in 10-membered thiolcarbonates (3) was successfully conducted by controlling the chairlike-boatlike transition states in the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates (2). The geometry of the product appeared to be highly dependent on the substituent pattern in the allylic system of the substrates (1). The 10-membered thiolcarbonates (3) were readily converted to (Z)- or (E)-allylic thiolcarbonates (11). Treatment of (Z)-3j or 3i with lithium in liquid ammonia afforded (Z)-trisubstituted or tetrasubstituted olefins (12j and 12i) in high yields.