Dihydrothiazine Oxides and Imines

During the past few years several groups have probed the conformations of [4 + 2] cycloadducts of iV-sidfinyl compounds and sulfur diimides. X-Ray crystallography has been particularly useful in this re- 

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There are several well-known transformations of 3,6-dihydrothiazine oxides and 3,6-dihydrothiazine imines. In most of these reactions, either the cyclic sulfinamide moiety and/or the carbon-carbon double bond is involved. For example, a 3,6-dihydrothiazine oxide can be hydrolyzed under either acidic or basic conditions to afford a homoallylic amine derivative [Eq. (17)]. 

The sulfur atom of both 3,6-dihydrothiazine oxides and 3,6-dihydro thiazine imines is readily attacked by nucleophiles other than water or hydroxide ion. Wucherpfennig has reported the cleavage of dihy-drothiazine oxides and dihydrothiazine imines with methoxide ion to afford sulfinate esters or imidosulfinate esters [Eq. (22)].54... 

The 3,6-dihydrothiazine 1-oxides and 1-imines are susceptible to ring cleavage with a variety of nucleophiles. Wucherpfennig investigated the S—N bond cleavage of 3,6-dihydrothiazine 1-oxides... 

In a similar fashion, 3,6-dihydrothiazine 1-imines can be cleaved by several alkyl and aryl organometallic reagents. Dihydrothiazine imines have more steric and electronic constraints compared to the corresponding oxides, and hence some are very resilient to ring opening by nucleophiles. Treatment of imine (80a) with phenylmagnesium bromide at — 60°C gave a product which was... 

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>. 

Two general classes of V-sulfinyl compounds have been employed as dienophiles. The most widely utilized type are N-sulfinyl species (115), formally monoimines of sulfur dioxide, which produce 3,6-di-hydrothiazine 1-oxides (116) (Scheme 14) upon cycloaddition. - -phe analogous bis-imines of sulfur dioxide (117) have also been used upon occasion as dienophiles to yield the 3,6-dihydrothiazine 1-imines (118). Both processes show excellent regioselectivity and are syn stereoselective with respect to the... 

The second aspect which is different in the case of the 3,6-dihydrothiazine 1-imines (80a) and (82a) as compared to the 1-oxide (73) involves the reactivity of the resulting allylic sulfilimine... 

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