Nitrone cycloaddition reactions in the micellar system

Abstract

A new cyclic nitrone, 4-Butyloxycarbonyl-3,4,5,6-tetrahydropyridine 1-oxide, has been synthesized. A study of stereo- and face-selectivity of the cycloaddition reactions of a series of mono- and disubstituted alkenes with the cyclic nitrone has been carried out. Rate constants for the cycloaddition of the nitrone to methyl acrylate, styrene, and methyl methacrylate have been determined at various temperatures by !H NMR spectroscopy. The addition reactions have displayed a very high degree of asymmetric induction; the cycloadducts were obtained with a face selectivity of-9:1. The remarkable exo/endo- and face-selectivity observed in our study reflects the scope inherent in these important cycloaddition reactions. The cycloaddition reactions of the cyclic nitrone in micellar media were carried out for the first time and were found to be very efficient. Conformational analysis and peracid induced ring opening of the cycloadducts to give the second-generation cyclic nitrones have been carried out. The piperidine-based nitrone was chosen because of its importance in the synthesis of piperidine alkaloids, which are widespread in nature. Conformational analysis has shed some light by which one can selectively generate the second generation nitrones efficiently.