Asymmetric Dihydroxylations of 1-Substituted (E)- and (Z)-3-Methylpent-2-en-4-ynes: Full Compliance with the Sharpless Mnemonic Re-established and Embellished

Abstract

Asymmetric dihydroxylations ("ADs") of the pentenynyl chlorides (E)- and (Z)-1 or the pentenyne-based ester (Z)-3 in the presence of (DHQ)(2)-containing ligands delivered diol stereoisomers (2R,3S)-2, (2R,3R)-2, and (3S,4R)-4, respectively. The ADs of pentenynyl ethers (E)-10 and (Z)-12, respectively, have the same stereochemical preference under analogous conditions; these reattributions correct previous reports of the contrary. The Sharpless mnemonic rationalizes all these results implying that each substrate prefers a Sharpless/Norrby instead of a Chapleur orientation in the transition state.