Derivatives of NPCl2(NSOCl) and (NPCl2)2 NSOCl. Part 19. Reactions of (NPCl2)2NSOCl with secondary amines

Abstract

Substitution reactions of (NPCl₂)₂NSOCl with pyrrolidine (Hpyr) or dimethylamine proceed according to a non-geminal pathway; the order of reactivity is PCl₂ > SOCl > PClR (R = pyr or NMe₂). The nucleophilic attack at the phosphorus centres preferably takes place from the oxygen side of the ring plane, resulting in a preponderance of the mono- and di-substituted derivatives which have their amino-group(s)cis with respect to the oxygen ligand. The substitution of the sulphur-bonded chlorine atom occurs with inversion of configuration and is probably attended by an important change in the geometry of the sulphur centre. The reactivity of the tri- and tetra-substituted compounds is dependent on the mutual position of the amino-substituents; if three amino-groups are placed at the same side of the ring plane, the compound is less reactive towards further substitution than its isomer(s), in which such an arrangement of substituents is not present. The ¹H n.m.r. spectra of the dimethylamino derivatives show the same additivity of mutual shielding of the amino-groups as previously observed for derivatives of (NPCl₂)₃ and cis-NPCl₂(NSOCl)₂. This can be considered as a strong support for the correctness of the structure assignments based on chemical considerations.