Stereo Selective Hydrogenation of (R)-(+)-Pulegone by Raney Nickel in the Presence of β-Cyclodextrin

摘要

Pulegone is present in many essential oils. Reduction of these oils by various reducing agents yields epimeric menthols. In mentho I alone, eight optically active isomers are possible. 1-Menthol (1 R, 2S, 5R) displays a minty, lightrefreshingodourwith an intense desirabie cooling sensation. The numbing effect creates the soothing of the throat desired in cough drops. It also has a cooling-anaesthetic effect and thus finds use in pharma and cosmetics. Catalytic hydrogenation with Raney nickel is of very great importance in chemical industry. In this communication we report the stereoselective and enantioselective effects of (3-cyclodextrin (BCD) and its derivatives, in the hydrogenation of (R)-(+)-pulegone with Raney nickel. In the presence of (3-cyclodextrin and its derivatives, the hydrogenation reaction of (R)-(+)-pulegone proceeded smoothly with high stereoselectivity for the formation of (1R, 2S, 5R)-menthol.