Conversion of Conjugated Enones into Enantiomerically Pure ‐Hydroxy Ketones or 1,3‐Diols – Samarium(II) Bromide Reductions of Protected ,‐Dihydroxy Ketones

Abstract

AbstractAsymmetric dihydroxylations of α,β‐unsaturated ketones in the presence of Sharpless' AD mix‐β™ delivered α,β‐dihydroxy ketones or, if phenylboronic acid was present, the corresponding phenylboronates. The Cα–O bonds of these species were removed at –78 °C – in the former case after acetonide formation, in the latter case directly – in an unprecedented manner, namely by treatment with a suspension of SmII bromide in THF/MeOH. The resulting monohydroxy ketones could be reduced if so desired to give syn‐ or anti‐configured 1,3‐diols. The same diols were produced in one‐pot reductions of the α,β‐dihydroxy ketone diacetonides with SmII bromide at 0 °C. When the α,β‐dihydroxy ketone phenylboronates were treated likewise, the phenylboronates of the 1,3‐diols were obtained. Diastereocontrol in the one‐pot reductions varied from perfect to nearly absent.