Sulfur diimide unsymmetrical

Several methods for the preparation of unsymmetrical sulfur diimides RN=S=NR have been developed. One approach involves the addition of a catalytic amount of an alkali metal to a mixture of two symmetrical sulfur diimides, RN=S=NR and RT8i=S=NR. A second method makes use of alkali-metal derivatives of [RNSN] anions.Eor example, derivatives in which one of the substituents is a fluoroheteroaryl group can be prepared by the reaction of the anionic nucleophile [RN=S=N] with pentafluoropyridine. Sulfur diimides of the type RN=S=NH (R = 2,4,6- Bu3C6H2S) have also been prepared. "... 

The adducts formed in these cases are the analogous dihydrothiazine imines 2. Symmetrical and unsymmetrical sulfur diimides are available, and both can act as heterodienophiles. In adducts 1 and 2 the sulfur center is chiral, and the implications of this fact will be discussed in some of the following sections. 

Various types of electron-deficient sulfur diimides react as hetero-dienophiles. In general, these cycloadditions occur under conditions similar to those used for AT-sulfinyl compounds. However, fewer types of sulfur diimides have been utilized in this process relative to Af-sulfinyl compounds. Some examples of symmetrical sulfur diimide Diels-Alder reactions are listed in Table l-II. It should again be noted that the orientational selectivity in these cycloadditions is the same as that shown by N-sulfinyl systems (cf. Table l-I). Several examples of cycloadditions with unsymmetrical sulfur diimides are shown in Table l-III. In all cases, these reactions were totally regioselective, and as noted above, reactions occurred at the least electron-deficient nitrogen-sulfur bond. Frontier molecular orbital (FMO) theory has been used to rationalize the regio-selectivity of addition of the cationic sulfur diimide shown in entry... 

Adducts of unsymmetrical sulfur diimides, in which the nitrogen atom in the heterocyclic ring bears an aryl substituent, undergo acidic hydrolysis to produce Af-aryl-substituted homoallylic amines (Scheme 1-XII). Alkaline hydrolysis of these adducts leads to A(-arylpyrroles, similar to the reaction shown in Eq. (21). ... 

Unsymmetrical sulfur diimides are commonly prepared by two methods. Treatment of a N, N -hw(arylsulfonyl)sulfur diimide with an equivalent of an amine leads to the displacement of one sulfonyl group [Eq. (6)].3... 

Alternatively, an amine and an N-substituted dichlorosulfimide will react to yield an unsymmetrical sulfur diimide [Eq. (7)].4... 

---