Aromatization of 3,5-diaryl-4,5-dihydroisoxazoles (la ~ le), 1,4- dihydropyridines (3a ~ 3c) and 1,3,5-triphenyl-4,5-dihydropyrazole (5) were promoted by tetrakis-pyridine nickel(ll) dichromate to yield the corresponding 3,5-diarylisoxazoles (2a ~ 2e) in moderate yields (52% ~ 72%), pyridine derivatives (4a ~ 4b) in moderate to high yields (79% ~ 88%) and 1,3, 5-triphenylpyrazole (6) in 81% yield, respectively. A one-pot procedure was developed to prepare the derivatives of indolizines 9a ~ 9b, lla ~ lib and 13 in moderate to high yields (84% ~ 93%) by the reaction of pyridinium JV-ylides, isoquinolinium iV- ylides or quinolinium iV-ylides with electron-deficient 8a~8b in the presence of tetrakispyridine nickel (II) dichromate (TPND). The results showed that TPND possesses very good activities on the aromatization of ^-containing heterocyclic compounds.

Key words: ISOXAZOLE P, PYRAZOLE P, PYRIDINE P, DEHYDROGENATION, AROMATIZATION