Photochemical EZ-isomerization of α,β-unsaturated amides and thioamides in the solid state

The solid-state EZ-isomerizability of α,β-unsaturated amides, which had low isomerizability in the solid state, was greatly improved by modifying their structure; EZ-isomerizability was attained by replacing the carbonyl group of the amides by a thiocarbonyl group as well as replacing the heterochiral N-substituent of the amides by a homochiral one. Crystallographic analyses have revealed that the isomerizability of α,β-unsaturated amides and thioamides in the solid state partially depends on their molecular conformation in crystal. In addition, it was found that the packing coefficient has a correlation with the isomerizability; a smaller value of the packing coefficient caused an increased formation of (Z)-isomers.