Stereoselective formation of activated cyclopropanes with pyridinium ylides bearing a (−)-8-phenylmenthyl group as the chiral auxiliary

✍ Scribed by Satoshi Kojima; Kouji Fujitomo; Yoshihiro Shinohara; Makoto Shimizu; Katsuo Ohkata

• Publisher: Elsevier Science
• Year: 2000
• Tongue: French
• Weight: 78 KB
• Volume: 41
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)01743-3

✦ Synopsis

The reaction of various mono-substituted methylidenemalononitriles with (-)-8-phenylmenthyl a-pyridiniumacetate in the presence of base afforded the corresponding dicyanocyclopropane compounds with exclusive trans-selectivity and good diastereoselectivity (up to 86:14). The stereochemistry of the major products were determined to be of 1R configuration by X-ray structural analysis of the crystalline trans-2,2-dicyano-3-(4-pyridyl)cyclopropanecarboxylate. The geometric and diastereofacial selectivities were rationalized assuming anti-periplanar approach in the open-chain model, followed by epimerization and then cyclization to give the cyclopropane compounds.