Preparation of free sulfoximines by treatment of N-tosylsulfoximines with sodium anthracenide

Since the discovery of the sulfonimidoyl function in 1949, sulfoximines and related derivatives of sulfonimidic acid have received considerable attenti0n.l A key feature is the variety of substitutions available to the sulfur-attached imino group. Unfortunately, direct methods for obtaining sulfoximines unsubstituted a t nitrogen have serious limitations. The standard procedure involves the reaction of a sulfoxide with hydrazoic acid in a mixture of sulfuric acid and chloroform2 (Scheme I, method A). In addition to the use of a potentially hazardous reagent: this method is limited to compounds having sulfur substituents that are incapable of forming stable carbonium ions; under the acidic reaction conditions heterolysis of a carbon+ulfur bond usually occurs in cases where the alkyl group is tertiary and to some extent in secondary c a ~ e s . ~ , ~ Treatment of a sulfoxide with 0-(mesitylsulfony1)hydroxylamine5 (MSH, method B) provides a general and mild alternate route. The method is limited since MSH is quite difficult to prepare and to handle.6 A useful indirect method is the cleavage of the tosyl (p-tolylsulfonyl) group of a N-tosylsulfoximine (1). These compounds are readily available by treatment of a sulfoxide with tosyl azide (or Chloramine-T in the case of dimethyl sulfoxide) in the presence of a copper(I1) salt4 (route 1). They may also be prepared by oxidation of N-t~sylsulfilimines~ with alkaline hydrogen peroxide? m-chloroperbenzoic acid (mCPBA) anion,g or sodium periodate-catalytic ruthenium dioxidelo (route 2). N-Tosylsulfoximines have been obtained by reaction of a sul