| Abstract
| - The diastereoselective tandem Michael−intramolecular Wittig reactions of a five-membered cyclicphosphonium ylide 2 using 8-phenylmenthyl enoates were examined. The reaction of thephosphonium ylide with 8-phenylmenthyl cinnamate followed by the hydrolysis of the resultingenol ether 4a afforded (3R,4S)-4-(diphenylphosphinyl)-3-phenylcycloheptanone (3R,4S)-5a as themajor isomer. The diastereoselectivity of the initial tandem reactions was estimated to be 94:6from the 31P NMR of a mixture of the diastereomeric ketal derivatives 6a and 6‘a which wereobtained by the reaction of 5a with (2R,3R)-2,3-butanediol, and the absolute configuration of themajor isomer was determined by the single-crystal X-ray analysis. Similar reactions using some8-phenylmenthyl alkenoates were attempted. As a result, it was clarified that the correspondingtrans-ketones 5b−d were obtained and that the diastereomer ratios of their ketal derivatives were60:40−73:27.
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