Asymmetric epoxidation of substituted chalcones and chalcone analogues catalyzed by alpha-D-glucose- and alpha-D-mannose-based crown ethers

作者：Mako Attila; Zsolt Rapi; Gyoergy Keglevich; Szollosy Aron; Drahos Laszlo; Laszlo Hegedus; Peter Bako^*

来源：Tetrahedron: Asymmetry , 2010, 21(8): 919-925.

DOI：10.1016/j.tetasy.2010.05.009

The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-alpha-D-glucopyrano-side-1 or mannopyranoside 2 have been applied as phase-transfer catalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetric induction. It was found that the position of the substituents in the aromatic ring of the chalcone had an influence both on the chemical yields and enantiomeric excesses. The lowest enantioselectivities (62-83% ee) were found in the case of ortho-substituted model compounds. The highest ee values (ee of 83-97%) were obtained in the case of para-substituted models. From among the chalcone analogues, the maximum ee (90-92%) was detected for the model compound having alpha-tert-butyl- and beta-aryl groups. Using glucose-based crown ether 1, formation of the (-)-enantiomer was preferred, while applying mannose-based 2 as the catalyst, the (+)-enantiomer was in excess.

• 出版日期2010-4-30