An Efficient, Stereoselective Approach to <i>s</i><i>yn</i>-1,2-Diols Protected as Cyclic Carbonates

Enantioenriched 4-hydroxyalk-2-ynyl carbonates (or benzoates) have been prepared by stereoselective zinc-mediated addition of alkyl 2-propynyl carbonates (or their benzoate analogues) to aldehydes. Their partial reduction to <i>Z</i>-olefins followed by cyclization under mild Pd-catalyzed conditions allowed a straightforward access to enantioenriched <i>syn</i>-1,2-diols protected as cyclic carbonates.