Imination sulfur compound

The synthesis of sulfoximides and sulfimides has attracted considerable attention in recent years due to the potential utility of these compounds as efficient auxiliaries and chiral ligands in asymmetric synthesis (reviews [86-88]). Transition metal-catalyzed nitrene transfer to sulfoxides and sulfides is an efficient and straightforward way to synthesize sulfoximides and sulfimides, respectively. Bach and coworkers reported the first iron-catalyzed imination of sulfur compounds with FeCl2 as catalyst and B0CN3 as nitrene source. Various sulfoxides and sulfides were... 

As the last point in Sect. IV, we discuss briefly the reactions of chiral sulfur compounds with electrophilic reagents. In contrast to nucleophilic substitution reactions, the number of known electrophilic reactions at sulfur is very small and practically limited to chiral tricoordinate sulfur compounds that on reacting with electrophilic reagents produce more stable tetracoordinate derivatives. It is generally assumed that the electrophilic attack is directed on the lone electron pair on sulfur and that the reaction is accompanied by retention of configuration. As typical examples of electrophilic reactions at tricoordinate sulfur, we mention oxidation, imination, alkylation, and halogenation. All these reactions were touched on in the section dealing with the synthesis of chiral tetracoordinate sulfur compounds. 

Aerobic oxidation is not going to be limited to alcohol oxidation. Apparently we are closer to finding suitable catalysts for alcohol oxidation, but oxidation of alkenes, aromatic hydrocarbons, alkylaromatics, imines, amines, sulfur compounds etc. will require much work in the forthcoming years. In some cases, the presence of radical initiators, even though in minor quantities, may serve to promote the oxidation catalyzed by noble metal nanopartides, and gold in particular [56, 108]. Thus, there is no doubt that the next years will witness exciting developments in the field of metal nanopartides for aerobic oxidation. 

Optically active sulfur containing compounds play a very important role in biochemistry as well as synthetic chemistry. The asymmetric conjugate addition of sulphur nucleophiles, or sulfa-Michael addition [379], provides a direct and versatile approach toward optically active sulfur compounds. This strategy is particularly valuable, since enantioselective nucleophilic additions to a C-S double bond, unlike those to carbonyls and imines, are not synthetically feasible. 

Their substrates are 2-phenylpyridines, imines, benzo[/i]quinones, phosphines, oxygen compounds, sulfur compounds, etc., as described in the previous sections or in Fig. 5.11, Tables 5.5 and 5.6. These reactions are arylations, alkenylations, alkylations, acylations, cyclizations, hydrogenations, oxidations, hydrosilylations, dehydrogenations, etc. 

It is well known that aziridination with allylic ylides is difficult, due to the low reactivity of imines - relative to carbonyl compounds - towards ylide attack, although imines do react with highly reactive sulfur ylides such as Me2S+-CH2-. Dai and coworkers found aziridination with allylic ylides to be possible when the activated imines 22 were treated with allylic sulfonium salts 23 under phase-transfer conditions (Scheme 2.8) [15]. Although the stereoselectivities of the reaction were low, this was the first example of efficient preparation of vinylaziridines by an ylide route. Similar results were obtained with use of arsonium or telluronium salts [16]. The stereoselectivity of aziridination was improved by use of imines activated by a phosphinoyl group [17]. The same group also reported a catalytic sulfonium ylide-mediated aziridination to produce (2-phenylvinyl)aziridines, by treatment of arylsulfonylimines with cinnamyl bromide in the presence of solid K2C03 and catalytic dimethyl sulfide in MeCN [18]. Recently, the synthesis of 3-alkyl-2-vinyl-aziridines by extension of Dai s work was reported [19]. 

Double asymmetric induction operates when the azomethine compound is derived from a chiral a-amino aldehyde and a chiral amine, e.g., the sulfin-imine 144 [70]. In this case, the R configuration at the sulfur of the chiral auxihary, N-tert-butanesulfinamide, matched with the S configuration of the starting a-amino aldehyde, allowing complete stereocontrol to be achieved in the preparation of the diamine derivatives 145 by the addition of trifluo-romethyl anion, which was formed from trifluoromethyltrimethylsilane in the presence of tetramethylammonium fluoride (Scheme 23). The substituents at both nitrogen atoms were easily removed by routine procedures see, for example, the preparation of the free diamine 146. On the other hand, a lower diastereoselectivity (dr 80 20) was observed in one reaction carried out on the imine derived from (it)-aldehyde and (it)-sulfinamide. 

Both compounds 190 and 193 are reduced to 9,10-diphenylanthracene (205) by zinc and acetic acid. However, more interest attaches to the formation of anthracenes from anthracen-9,10-imines in nonreducing conditions. The iV-ethoxycarbonyl derivative (192) decomposed at 215° in cyclohexane to 33% of 205, although curiously this product was not obtained if the solvent was previously degassed. Whether or not the reaction involves simple extrusion of ethoxycarbonyl nitrene could not be established, since the expected iV-cyclohexylurethane was not detected. The 9,10-epithioanthracene (194) loses sulfur thermally to give 205. ... 

An overall strategy for the synthesis of 1,2,5-thiadiazoles from the acyclic N-C-C-N grouping and sulfur monochloride was proposed in 1967 (1967JOC2823). The N-C function could vary over oxidation levels of amine, imine, cyanide, oxime and nitroso derivatives. Aliphatic and aromatic compounds having these functionalities in many combinations reacted with sulfur monochloride to form appropriately substituted or fused 1,2,5-thiadiazoles. Based on this model, a large... 

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