Synthesis of 1,2-Diols and Their Base-Initiated Rearrangement to Butyrolactones

1,2-Diols 3 have been synthesized by the aldol addition of hydroxy esters 1 to propargyl aldehydes 2 in dichloromethane. These 1,2-diols undergo a base-initiated rearrangement under mild conditions in methanol with an unusual 1,2-alkyl shift to afford interesting alpha,beta-unsaturated gamma-butyrolactones 4. A possible mechanism is postulated on the basis of experimental evidence and the results of DFT calculations.