Sulfur Diimide Cycloadditions

Various types of electron-deficient sulfur diimides react as hetero-dienophiles. In general, these cycloadditions occur under conditions similar to those used for Af-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 1-1). Several examples of cycloadditions with unsymmetrical sulfur diimides are shown in Table 1-111. In all cases, these reactions were totally regioselective, and as noted above, reactions occurred at the least electron-deficient nitrogen-sulfiir bond. Frontier molecular orbital (FMO) theory has been used to rationalize the regio-selectivity of addition of the cationic sulfiir diimide shown in entry 12.  

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These A-sulfinyl Diels-Alder reactions are also highly stereoselective, giving products of syn addition to the 1,3-diene. The same holds true for the sulfur diimide cycloadditions . The stereoselectivity with respect to the dienophile is not very well known because the stereochemistry of sulfur in the starting A-sulfinyl dienophile and in the resulting thiazine derivatives has usually not been determined. A representative sample of the stereoselective preparation of 3,6-dihydrothiazine 1-oxides and 1-imines is shown in Scheme 34 <84JA786i, 84JA7867>. 

Kresze has written several excellent reviews on 7V-sulfinyl and sulfur diimide cycloadditions. This chapter will concentrate most heavily on the more recent developments in the area, and previous summaries should be consulted for additional information. 

Mock and Nugent investigated the, reaction of N,A( -bis(p-toluene-sulfonyl)sulfur diimide (18) and the isomeric 2,4-hexadienes 10,11, and 12 in an attempt to elucidate the mechanism of sulfur diimide cycloadditions (Scheme 1-IV)." The cycloaddition of 18 and 10 afforded two adducts epimeric at sulfur in a 43 1 ratio, while only one adduct of indeterminate stereochemistry was obtained from the cycloaddition of 18 and 11. No reaction was observed with (Z,Z)-diene 12. Unfortunately, not enough information resulted from these experiments to draw any mechanistic conclusions with regard to the cycloaddition. 

The N—S—N grouping in the [3 -1- 2] (type A) thiadiazole syntheses is functionally equivalent to either an N,N - or S,.S -disubstituted sulfur diimide, diaminosulfane, sulfamide or tetrasulfur tetranitride. In the cycloaddition of diphenylketene to A,fV -diphenylsulfur diimide the 1 1 adduct... 

Ligated Tj -allyl compounds (Scheme 21) can react with sulfur diimides, e.g., 216 reacts with sulfur bis(methanesulfonylimide) to give the iron complex 217. The [3 + 3] cycloadduct may possibly result from initial [3 + 2] cycloaddition followed by rearrangement (83MI3 86MI4). 

The preparation of 3,6-dihydro-1,2-thiazine 1-oxides by [4 + 2] cycloaddition of iV-sulfinyl compounds has been intensively studied since the mid-1980s . The [4 + 2] cycloaddition of iV-sulfinylaniline with 1,3-dienes was first reported in 1953. Since then, a number of Diels-Alder cycloadditions of iV-sulfinyl compounds and the related sulfur diimides have been reported. These cycloadditions usually proceed expeditiously, often exothermically, at... 

The resulting iV-sulfinyl derivatives can often be distilled and/or crystallized but are water sensitive and thus are frequently prepared in situ for subsequent cycloaddition reactions. Symmetrically substituted sulfur diimides can usually be prepared by the reaction of SCI2 or S2CI2 with the parent NH2 compound in the presence of a base such as pyridine or triethylamine [Eq. (4)]. ... 

Levchenko and Balon" have examined the regiochemistry of cycloaddition of several symmetrical bis(aryl)sulfonyl sulfur diimides with ( )-piperylene and isoprene which afforded the C-3 and C-5 substituted adducts, respectively (Scheme l-III). These results were confirmed by Wucherpfennig and Kresze, who also found that chloroprene gave the 5-substituted product. ... 

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