THE EFFECT OF SUBSTITUENTS ON THE PYRIDINE RING IN THE DIASTEREOSELECTIVE CYCLOPROPANATION REACTION OF PYRIDINIUM YLIDES BEARING AN 8-PHENYLMENTHYL ESTER GROUP

摘要

The reaction between bera-substituted methylidenemalononitriles and the ylide from(-)-8-phenylmenthyl alpha-pyridiniumacetate,which affords activated cyclopropanes bearing two cyano groups and one carboxylic ester group,was examined.The trans isomer was obtained in up to 91:9 diastereoselectivity under optimized solvent conditions for the t-butyl substituted substrate.The selectivity increased to 96:4 upon using 4-methoxypyridine in the place of pyridine,whereas selectivities were generally lower for N,N-diethylnicotinamide.The major 4-pyridyl substituted cyclopropane was determined to be trans-1R by X-Ray structural analysis.