Sulfur imido complexes

The mechanistic nature of these nitrene insertion reactions remains unknown. A number of possible routes can be considered (Fig. 302), including (1) direct insertion, (2) initial formation of a metal-nitrene (imido) complex followed by insertion, (3) initial addition of nitrene fragment to sulfur (i.e., oxidation of sulfur) followed by an isomeric rearrangement. On the basis that copper(II) nitrene complexes are unknown (although they have been implicated in the copper-catalyzed aziridination process) this route is ruled out and literature precedent suggests that route (3) is most likely. 

Taurine is generally prepared from ox bile1 or the large muscle of the abalone.2 It has been synthesized from isethionic add through chloroethanesulfonic acid followed by the action of aqueous ammonia 3 from ethyleneimine and sulfur dioxide 4 from 2-mercaptothiazoline by oxidation with bromine water 5 from bromoethylamine and ammonium sulfite 6 and from acetaldehyde by a complex set of reactions involving sulfonation, formation of the aldehyde ammonia and the imido sulfonic add and finally reduction.7 The method given in the procedure has recently appeared in the literature.8 9... 

While all of the transformations detailed above take place at low-valent metal centers, a double sulfur-carbon bond cleavage process has also been postulated to occur at the molybdenum(VI) center (527, 528, 839). Thus, thermolysis of organic isocyanates with [Mo02(S2CNR2)2] affords imido-disulfide complexes, [Mo(NR )(S2)(S2CNR2)2] (Fig. 289), in moderate yields. The fate of the aminocarbyne fragment remains unknown and further, since monosulfido... 

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