Semiempirical calculations in a search for a mechanism of 2-methyl-4-phenylquinoline formation from 4,4-diphenyl-3-buten-2-one oxime acetate

The known thermal non-catalytic formation of 2-methyl-4-phenylquinoline fro m 4,4-diphenyl-3-buten-2-one oxime acetate was analyzed by semiempirical MN DO, AMI and PM3 methods of calculation, assuming the process consists of th ree steps: thermal disrotatory electrocyclization of the oxime acetate, inv ersion of the cyclic intermediate on the nitrogen atom and elimination of a cetic acid from the inverted intermediate according to E-i mechanism. It ap pears from PM3 calculations, which led to better results than MNDO or AM1, that the disrotatory electrocyclization is the rate-determining step for th e whole synthesis.