v-triazolines.: Part 40.: Thermal and photochemical transformations of 1-biaryl-5-amino-4,5-dihydro-v-triazoles a new synthetic approach to 6-alkylphenanthridines and aza-analogs

1-Biaryl-5-morpholino-v-triazolines 4 were prepared from aliphatic aldehydes 1, morpholine and 2-azidobiaryls 3. They underwent smooth; thermal rearrangement to tertiary amidines 5 which were photochemically cyclized to 6-alkylphenanthridines 6a,b,e,f and analogs 6c,d and 8a,b with morpholine elimination. Direct photolysis of triazolines 4 afforded lower yields of the same compounds 6 together with by-products indicative of the mechanism of the photochemical rearrangement which is discussed.