NITROALKENE [4-DISUBSTITUTED AND 3,4-DISUBSTITUTED PYRROLIDINES(2] CYCLOADDITION AS A GENERAL AND STEREOSELECTIVE ROUTE TO THE SYNTHESIS OF3,3)

2,2-Disubstituted 1-nitroalkenes 12 undergo Lewis acid-promoted [4 + 2 ] cycloadditions with n-butyl vinyl ether to afford cyclic nitronates 14 as anomeric mixtures in good yields. The resulting nitronates were reduced with hydrogen in the presence of Adam's catalyst to afford 3,3 -disubstituted pyrrolidines which were isolated in good yield as their N-p-toluenesulfonamides 17. Cycloadditions of (E)-2-nitrostyrene with ethyl (E)- and (Z)-1-propenyl ethers provided for the stereoselective synthesis of cis- and -3-phenyl-4-methyl-N-(p-tolylsulfonyl)pyrrolidi ne. Similarly, trans-3,4-diphenyl-N-(p-tolysulfonyl)pyrrolidine was pr epared from (E)-2-nitrostyrene and ethyl (E)-2-styryl ether.