PHOTOCHEMICAL ISOMERIZATION OF N-MONOSUBSTITUTED ALPHA,BETA-UNSATURATED THIOAMIDES TO IMINOTHIETANES

Photochemical isomerization of thiomethacryl-, thiotiglyl-, and thiocrotonamides gives iminothietanes, N-(2-thietanylidene)amines, in good yields. The iminothietanes reverted quantitatively to the starting materials on heating. Use of Michler's ketone or thioxanthone as sensitizers indicates that the photoelectric cyclization proceeds from the triplet excited state. Irradiation of N-benzylthiocinnamamide does not give an iminothietane, but only cis-trans isomerization that reached the photostationary state at cis/trans = 1.7.