Wedekind–Fock–Havinga salt Me(Et)N+(All)PhI– · CHCl3 as historically the first object for absolute asymmetric synthesis: spontaneous resolution, structure and absolute configuration.

Abstract

The title salt crystallises as a conglomerate (space group P2 ₁2₁2₁, Z = 4) with one solvate CHCl₃ molecule forming strong shortened contact with I^– [Cl‥I^– 3.599(2) Å]. Therefore, it undergoes spontaneous resolution by simple crystallisation with a deficiency of the conglomerator CHCl₃ or by an internal entrainment procedure. It exhibits the (S)–(+) absolute configuration and racemises in solution (ΔG^# rac= 26.5 kcal mol^–1). The salt was almost completely converted into one enantiomer by stirred crystallisation from solution (with full evaporation) or from a melt under conditions of enantiomerisation. The contribution of autocatalysis to this process is discussed.