Photocleavage reactions of monothioimides

Article abstract of DOI:10.1107/S0108270197011645

The photochemistry and crystal structures of four monothioimides have been studied: N-phenyl-3-phenyl-N-[phenyl(thiocarbonyl)]propanamide, C₂₂H₁₉NOS, (1a); N-(4-bromophenyl)-N-[phenyl(thiocarbonyl)]-3-phenylpropanamide, C₂₂H₁₈BrNOS, (1b); N-(4-bromo-2,6-dimethylphenyl)-3-phenyl-N-[phenyl(thiocarbonyl)]-propanamide, C₂₄H₂₂BrNOS, (1c); and N-[4-methoxyphenyl(thiocarbonyl)]-N-phenyl-3-phenylpropanamide, C₂₃H₂₁NO₂S, (1d). All four molecules adopt similar (E_s,Z_o) conformations, which are not suitable for photo-chemical γ-hydrogen abstraction; short intramolecular O...C(S) contacts (2.8 A) suggest a new mechanism with nucleophilic attack by the carbonyl O atom on the C=S double bond; the presence of water is also essential for the reaction to proceed.