Detailed studies of the interaction of 3-chloroaniline with O,O′-diphenylphosphorylisothiocyanate

Abstract

The reaction of neat 3-chloroaniline with neat SCN–P(O)(OPh)₂ leads to a new N-phosphorylated thiourea, 3-ClC₆H₄NHC(S)NHP(O)(OPh)₂ (1). The same reaction in non-dried CH₂Cl₂ or C₆H₆ leads to the salt-like compounds [3-ClC₆H₄NH₃]⁺[NCS]⁻ (2) and [3-ClC₆H₄NH₃]⁺[P(O)₂(OPh)₂]⁻·0.5C₆H₆ (3·0.5C₆H₆), respectively, while using non-dried acetone yields 1-(3-chlorophenyl)-4,4,6-trimethyl-3,4-dihydropyrimidine-2(1H)-thione (4). Dissolution of 1 in non-dried CH₂Cl₂, C₆H₆ or Me₂CO leads to the direct formation of 2, 3·0.5C₆H₆ and 4, respectively. It was established that thione 4 is most likely formed through the thiourea 1-assisted aldol condensation of acetone leading to mesityl oxide. In turn the latter ketone interacts with 1 followed by its hydrolysis leading to 4. Compounds 1–4 have been characterized by NMR spectroscopy and elemental analysis and their molecular structures were elucidated by X-ray diffraction. Hirshfeld surface analysis showed that the structures of both 1 and 4 are mainly characterized by H⋯H, H⋯C, H⋯Cl and H⋯S contacts as well as by H⋯O in the structure of 1. The enrichment ratio, derived as the decomposition of the crystal contact surface between pairs of interacting chemical species, for 1 was found, as expected for the polar contacts, which are generally hydrogen bonds, to be significantly larger than unity for the contacts of the type H⋯O and H⋯S. A much larger than unity value was found for the enrichment ratio of the C⋯C contacts in the structure of 1, which is due to extensive π⋯π stacking in the crystal packing. The enrichment ratio for 4 was found to be larger than unity for the contacts of the type H⋯C and, but with a lesser degree, H⋯Cl and H⋯S.