ASYMMETRIC MICHAEL ADDITION OF 2-NITROPROPANE TO A CHALCONE CATALYZEDBY CHIRAL CROWN-ETHERS INCORPORATING A D-GLUCOSE UNIT

Michael addition of 2-nitropropane 4 to a chalcone 3 catalyzed by crow n ethers incorporating two glucose units (of 1 type) afforded the addu ct 5 with an R-enantiomer excess (28% ee) while the aza-crown ethers c ontaining one glucose unit (of 2 type) gave the same adduct favoring t he S-enantiomer under solid-liquid phase transfer conditions (SL-PT). It was proven that substituents at the N-atom of the crown ring in 2 h ave a significant effect on both the chemical yield and the enantiosel ectivity, and those having heteroatoms in the proper position of the s ide chain (2e, 2f) showed the best results in this reaction: 65% ee fo r the S-antipode. The absolute configuration of (+)-4-methyl-4-nitro-1 ,3-diphenyl-1-pentanone (5), determined by X-ray diffraction, is also presented in this article. (C) 1997 John Wiley & Sons, Inc.