Synthesis of chiral alk-1-ynes containing an α-phenylethyl group

Abstract

(R)-4-Phenylpent-1-yne, (R)-(1b), and (S)-5-phenylhex-1-yne, (S)-(1c), have been synthesised from the corresponding chiral alk-1-enes (2) by a stereospecific bromination–dehydrobromination procedure. On the other hand, (R)-3-phenylbut-1-yne, (R)-(1a), has been prepared in high enantiomeric purity by conversion of the racemic alkyne into (RS)-4-phenylpent-2-ynoic acid (7), followed by resolution and decarboxylation of the (+)-acid. A convenient synthetic route to the racemic alkyne (1a) is also described.