SYNTHESIS AND AZA-[2,3]-WITTIG REARRANGEMENTS OF VINYLAZIRIDINES - SCOPE AND LIMITATIONS

cis- and trans-2,3-Trisubstituted vinylaziridines have been prepared f rom cis- and trans-epoxy alcohols, respectively, and used as substrate s in the aza-[2,3]-Wittig rearrangement. Five different anion-stabiliz ing groups have been investigated for their efficiency to promote the rearrangement, and it was found that N-tert-butyl acetyl vinylaziridin es were superior in this reaction, affording the corresponding cis-2,6 -tetrahydropyridines (>90%) as single isomers when treated with LDA. S imilarly, the corresponding (Z)-propenylaziridines gave trans,trans-2, 3,6-trisubstituted tetrahydropyridines as the sole products while the (E)-propenylaziridines afforded the cis,cis-2,3,6-derivatives with equ ally high selectivity. The scope and limitations of the process have b een investigated by varying the structure of the substrate, and the me chanism of the rearrangement has been probed to some extent; the mecha nistic picture is more complex than assumed previously.