Studies on Pd(0)-catalyzed cyclization of N-3,4-alkadienyl toluenesulfonamides with organic halides: selective synthesis of 2,3-dihydropyrroles, 1,2,3,6-tetrahydropyrridines, and azetidines.

The palladium-catalyzed coupling-cyclization of beta-amino allenes with organic halides ranging from aryl halide to 1-alkenyl halide was studied. 2,3-Dihydro-1H-pyrroles were obtained by reaction of 3-substituted-5-unsubstituted-3,4-allenyl amides under conditions A, while the reaction of 5-substituted-3,4-allenyl amides afforded 1,2,5,6-tetrahydropyridines and/or azetidines with high de under conditions B or C. The skeleton and relative configuration of the six-membered products were established by the X-ray diffraction studies of 10 ka. Allenyl amide 4 q reacted with 1,4-diiodobenzene 6 r to afford double cyclization product 15. The structure of its major stereoisomer was also determined by the X-ray diffraction study.