Allylic sulfimide 2,31-rearrangements

An alternative to the Bach procedure (BocN3/FeCl2) for the synthesis of Boc-protected sulfimides was developed in 2002 (Scheme 76) [171]. Oxaziri-dine 312, prepared from diethyl ketomalonate, was found to iminate allylic sulfides 309 at low temperatures. The resulting allyl sulfimide (not shown) immediately rearranged to protected amines 313 in high yields. The possibility of preparing a-amino acid derivatives like 314 is a noteworthy feature although the compounds are, of course, racemic. 

Scheme 18.67 Preparation and rearrangement of chiral allylic sulfimides.—...

Uemura and co-workers (91) demonstrated that copper catalysts effectively transfer nitrenoid groups to sulfides generating chiral sulfimides. A complex obtained from CuOTf and 55d catalyzes nitrenoid transfer to prochiral sulfides to afford products such as 139 in moderate to poor enantioselectivities (<71% ee, Eq. 78). Nitrenoid transfer occurs selectively to the sulfur atom of allylic sulfides generating allylic sulfenamide (140) in moderate selectivity, after [2,3] sigmatropic rearrangement of the initial sulfimide 141, Eq. 79. 

Besides commonly used TsN=IPh, TsNs can also be employed as a nitrene source. Bach and Korber have recently reported an Fe(iii)-catalyzed imidation of allyl sulfides 200 with iV-/ //-butyloxycarbonyl azide (BocNs), followed by [2,3]-sigmatropic rearrangement (Scheme 21). " The azide reacts with FeCl2 to generate Fe(iv) nitrene complex 201, which then reacts with allyl sulfide 200, to give an intermediate sulfimide 203, presumably through Fe(iii) intermediate 202. 

Allylic sulfides can be transformed by a 2,3-sigmatropic rearrangement into allylic nitrogen derivatives (equation 26) via a sulfimide intermediate (Scheme 36). ° ° ... 

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