Preparation of N,N'-Dialkyl bis(diamino) diphenylmethanes and N,N'-Dialkyl bis(diamino) benzophenones: preparation of B-hydroxy sulfonamides and B-hydroxy sulfinamides

Abstract

N,N'-Dimethyldiaminodiphenylmethanes and N,N'-dialkyldiaminobenzophenones were successfully prepared from the respective primary amines via alkylation of their methanesulfonamide derivatives. Initially N,N'-diaminodiphenylmethanes and N,N'-diaminobenzophenones were treated 0 with 2.2 equivalents of methanesulfonyl chloride in pyridine at 80° to afford the corresponding bis methanesulfonamide derivatives in 79-91% yields. Alkylation was accomplished by reacting the sulfonamides with 2.2 equivalents of dry potassium hydroxide in hexamethylphosphoramide at 75°, followed by addition of 2.2 equivalents of alkylating agent (methyl iodide, ethyl iodide, and benzyl chloride) to afford 70-84% of the alkylated sulfonamides. Subsequently the N,N'-dialkylsulfonamides were cleanly cleaved using a mixture of concentrated sulfuric/acetic acids (40-60%, vol/vol) to afford N,N'-dimethyldiaminodiphenylmethanes and N,N'-dialkyldiaminobenzophenones in 68-87% and 64-85% yields, respectively. β-Hydroxy sulfonamides were prepared by treating N-methyl methanesulfonanilide with a 10% excess of n-butyllithium in tetrahydrofuran at -78°, followed by addition of benzophenone or acetone to afford the corresponding β-hydroxy sulfonanilides in 76% yield. Upon heating the sulfonanilide-benzophenone adduct in refluxing toluene, water was eliminated to form the corresponding unsaturated sulfonanilide in 89% yield. The attempted preparation of β-hydroxy sulfinamides involved initially the synthesis of N-methanesulfin-p-toluidide following the procedure of Corey and Durst. This compound was subsequently alkylated with sodium hydride and methyl iodide in 1.2-dimethoxyethane in 76% yield. Treatment of the resulting methylated sulfinamide with lithium 0 diisopropylamide at - 78° followed by addition of water, resulted in elimination of the methanesulfine group to afford N-methyl-p-toluidine as the major product.