Photoisomerisation of substituted 2-methylpyridines to ortho-substituted anilines

Abstract

2-Methylpyridines substituted in the side chain [2-PyCH₂X (1)(X = CN, CO₂Me, or Ph)] photoisomerised to the corresponding anilines in moderate yields. The four ethyl methyl-2-pyridylacetates (3a–d) were prepared and irradiated. Except for the 6-methyl isomer (3d), they rearrange to ethyl methylanthranilates (4a–c) through exchange of the ring nitrogen atom with the side chain carbon. The photoreactivity of (3d)(6-Me) is low in contrast with the other acetates; the quantum yields (ϕ_decomp.) for the disappearance of starting materials are: (3a) 0.25, (3b) 0.18, (3c) 0.09, and (3d) 0.006 7. The multiplicity of the reactive state is discussed.