Conformation of Methyl trans-3-Arylpropenoates in Triplet States and Their Reactivities

Abstract

Abstract The photochemical cis–trans isomerization and cycloaddition of methyl trans-3-arylpropenoates in benzene via triplet state were investigated. The results of triplet sensitized cis–trans isomerization clearly indicated that the most stable conformation for methyl 3-phenylpropenoate is a twisted form while methyl 3-(4-biphenylyl)propenoate and methyl 3-(2-naphthyl)propenoate are in the equilibrium states between the trans-planar triplet and twisted form. Photoirradiation of these methyl 3-arylpropenoates in relatively high concentrated benzene solutions gave two isomeric cyclodimers of dimethyl t-3, t-4-diaryl-r-1, c-2-cyclobutanedicarboxylate and dimethyl c-3, t-4-diaryl-r-1, t-2-cyclobutanedicarboxylate as main products. The reactivities of cycloaddition are relatively high where the most stable conformation is twisted form.