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Diastereoselective Vinyl Phosphate/β-Keto Phosphonate Rearrangements

1996; American Chemical Society; Volume: 61; Issue: 12 Linguagem: Inglês

10.1021/jo9518157

1520-6904

Jianguo An, J. M. WILSON, Yi-Zhong An, David F. Wiemer,

Phosphorus compounds and reactions

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.