Transannular S...N interactions in 10-ethynyl-10H-phenothiazine 5-oxide and 5,5-dioxide

Abstract

The title compounds, C14H9NOS, (1), and C14H9NO2S, (2), are oxidation products of the parent compound 10-ethynyl-10H-phenothiazine. They differ with respect to transannular interactions, the intramolecular S...N contact being shorter in (2). Intermolecular Csp—H...O hydrogen bonds were detected in both crystals, and (1) was found to form stronger hydrogen bonds. These results are in agreement with the lower acidity of Csp—H in (2), caused by an increase in π-electron density due to the transannular S...N interaction.