The first regio-and diastereoselective synthesis of homochiral perhydroimidazoisoxazoles via the 1,3-dipolar cycloaddition of imidazoline 3-oxides with (1S)- (-)-beta-pinene

Abstract

The 1,3-dipolar cycloaddition of imidazoline 1-oxides I with (1S)-(-)-beta -pinene proceeds regio- and diastereoselectively to give homochiral perhydroimidazoisoxazole derivatives 3 in high yields in the cases of imidazoline 3-oxides 1a-e but in low yields in the reactions of If g. The preferred attack of (1S)-(-)-beta -pinene to the cyclic nitrone was shown to be anti-endo. The reaction of racemic nitrones (+/-)-1f g with the homochiral beta -pinene gave the adduct from (lie (S)-nitrone and the corresponding imidazole. The adducts 3 Undergo retro-1,3-dipolar cycloaddition when heated in the condensed phase or in diphenyl ether to give the corresponding imidazole and beta -pinene.