title: Diastereoselective Vinyl Phosphate/beta-Keto Phosphonate Rearrangements.
abstract: Several nonracemic diols and amino alcohols have been tested for their utility as chiral auxiliaries in vinyl phosphate/beta-keto phosphonate rearrangements. When (2R,4R)- or (2S,4S)-pentane-2,4-diol were employed, the diastereomeric beta-keto phosphonates obtained from three prochiral cyclohexanones gave separate resonances in their respective (31)P NMR spectra, allowing estimation of diastereomeric excess (de) via straightforward integration. A crystalline enol form of the beta-keto phosphonate was obtained from one ketone (4-(1,1-(ethylenedioxy)ethyl)-4-methylcyclohexanone, 10), which allowed determination of its absolute stereochemistry by X-ray diffraction analysis. When LTMP was used to induce rearrangement of vinyl phosphates derived from ketone 10 and (2R,4R)- or (2S,4S)-pentane-2,4-diol, a de of 2.5:1 was obtained. In addition, de values of 2.0:1 and 1.4:1 were obtained with parallel rearrangements of 4-isopropyl- and 4-methylcyclohexanone, suggesting that this sequence may be more generally applicable to preparation of nonracemic materials from prochiral cyclohexanones.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, Iowa 52242-1294.
authors.forename: Jianguo
authors.initials: J
authors.lastname: An
authors.forename: Jeffrey M.
authors.initials: JM
authors.lastname: Wilson
authors.forename: Yi-Zhong
authors.initials: YZ
authors.lastname: An
authors.forename: David F.
authors.initials: DF
authors.lastname: Wiemer