ONE-FLASK, CONSECUTIVE [3,3] AND [2,3] SIGMATROPIC REARRANGEMENTS FOR CONVERSIONS OF PROPARGYLIC ALCOHOLS INTO 2-CARBON-EXTENDED 4-OXO-2-ALKENOATE ESTERS - USE OF A NEW 1-CHLORO-1-ETHOXY-2-SULFINYLETHYLENE

Seven differently substituted primary and secondary propargylic alcohols are shown to react with (arylsulfinyl) vinylic chloride 1a at 100-degrees-C for 1 h sequentially via a [3,3] sigmatropic rearrangement and then a [2,3] sigmatropic rearrangement to form 4-oxo-2-alkenoates 8a-8e and 9a and 9b in 52-80% yields. This one-flask, intramolecular carbon-carbon bond-forming process represents a simple and convenient method not only for regiospecific gamma-attachment onto a propargylic alcohol of a two-carbon (ethoxycarbonyl)methylene unit but also for alpha --> beta transposition of oxygen. The synthetic utility of this procedure is illustrated further by eqs 2 and 3 for preparation of regiospecifically functionalized carbocycles and heterocycles. Also, two different primary allenic allylic alcohols are shown to produce directly two-carbon extended 3-(hydroxyalkyl)-2,4-pentadienoates (E)-18 and the corresponding unsaturated lactones (Z)-18 in 37-41% yields.