X-Ray Crystal Structure and Photo Chemistry of N-Methyl-N-(1-phenylvinyl)benzamide

Abstract  

N-methyl-N-(1-phenylvinyl)benzamide (I) has empirical formula C₁₆H₁₅NO, crystallizes in the monoclinic space group, P21/n, with unit cell parameters a = 8.9101(2) ?, b = 15.1416(4) ?, c = 9.7737(2) ?, α = 90°, β = 109.3320(10)°, γ = 90°, Z = 4. Interestingly, the Compound (I) undergoes photocyclization upon irradiation of light to give two cyclic lactams (A and B) below 3100 ?. Compound (I) can be cyclized at either of two equivalent ortho positions. The mechanism for formation of lactam A may involve electrocyclic ring closure reaction upon irradiation of light to give six-membered cyclic zwitterionic intermediate. The ring proton rearranges via [1, 5]-H shift to give isomerized product A. The minor photoproduct B is supposed to be formed via photocyclization process followed by a loss of proton and the tautomerized product undergoes oxidation for the revival of aromaticity.