Synthesis, X-ray Structure and Photo Chemistry of 2-(Methyl(1-Phenylvinyl)Carbamoyl)Phenyl Acetate

摘要

Abstract 2-(Methyl(1-phenylvinyl)carbamoyl)phenyl acetate (SM), empirical formula C₁₈H₁₇NO₃, crystallizes in the triclinic space group, P−1, with unit cell parameters a = 9.10870(10) Å, b = 10.56940(10) Å, c = 16.1340(2) Å, α = 78.0590(10)°, β = 89.5080(10)°, γ = 86.6830(10)°, Z = 4. The 2-(methyl(1-phenylvinyl)carbamoyl)phenyl acetate (SM) molecule, upon irradiation of UV-light below 3,000 Å, releases acetate group to give six membered cyclic lactam 1 as the major product. The quantum yield for the lactam 1 was found to be 0.053. An alternate conrotatory 6-pi electron photochemically allowed electrocyclic ring closure reaction also occurs upon irradiation to give a six-membered cyclic zwitterionic intermediate which retains acetate as leaving group. A [1,5]-H shift would then give the isomerized product 2. The quantum yield for the lactam 2 was found to be 0.026. A minor oxidation product lactam 3 that retains the leaving group also formed, likely from loss of a proton and tautomerization of enol. The loss of one hydrogen molecule is the driving force for revival of aromaticity in the minor product 3. The quantum yield for the lactam 3 was found to be 0.012. The low value of total quantum yield (0.091) for photocyclization of SM can be explained as the photoproducts absorb light in competition with the photoreactant.