Addition of Diethylzinc to Dicobalt Hexacarbonyl Complexes of <i>α</i><i>,</i><i>β</i>-Acetylenic Aldehydes with Virtually Complete Enantioselectivity. A Formal Synthesis of (+)-Incrustoporin

Abstract

[reaction: see text] The addition of diethylzinc to dicobalt hexacarbonyl complexes of acetylenes mediated by (R)-2-piperidino-1,1,2-triphenylethanol takes place with very high enantioselectivity (96-99% ee) to afford the S enantiomers of dicobalt hexacarbonyl complexes of 1-alkynyl-1-propanols. The utility of this process is exemplified by the development of a short, highly enantioselective (99% ee) synthesis of unnatural incrustoporin.