Optically active (R)-(propargy1oxy) acetic esters 5, available in ca. 90% ee through reduction of alkynones 2 with Chirald-LiAlH4 followed by alkylation with chloroacetic acid and esterification with CHSNZ, undergo highly stereoselective [2, 3] rearrangement upon treatment with LDA in THF at-78 OC followed by CpzZrC19 to afford a (s)-hydroxy-B (R)- allenic eetsrs 7 with complete transfer of chirality and> 90% diaatereoeelectivity. Upon ...
