NUCLEOPHILIC DISPLACEMENTS ALPHA TO SULFONYL GROUPINGS

Thiophenoxide ion in dimethylformamide solution displaces the halogen atom in halomethyl and α-halobenzyl phenyl sulfones to give high yields of the corresponding phenylthiomethyl and α-phenylthiobenzyl phenyl sulfones. A study of the effect of the nature of the halogen (bromine or chlorine) and the effect of protic solvents on the proportion of displacement vs. reduction products was made. Thiophenoxide ion in either dimethylformamide or 33% methanol-67 % dimethylformamide solvents reacted with halomethyl phenyl sulfones to give a nearly quantitative yield of phenylthiomethyl phenyl sulfone (2). In ethanol solution, thiophenoxide ion reacted with the halomethyl phenyl sulfones to give ca. 80% 2 and 20% methyl phenyl sulfone (3). In the reaction of thiophenoxide ion with α-halobenzyl phenyl sulfones, α-phenylthiobenzyl phenyl sulfone was obtained in anhydrous dimethylformamide, while this same reaction in the presence of small amounts of protic solvent gave large amounts of benzyl phenyl sulfone (7). It is concluded that the halomethyl phenyl sulfones are undergoing Sn2 reactions but that the α-halobenzyl phenyl sulfones are probably reacting by a reduction-displacement sequence. © 1968, American Chemical Society. All rights reserved.