Disulfide intermediate formation

The reaction was apparently initiated by N-sulfenylation and the possible intermediate formation of 1,2,3-dithiazolidine 193 followed by the addition of the second diamide molecule with the formation of disulfide 194 and a final rearrangement to tetrathiane 192. 

The reaction of perfluorobenzonitrile with carbon disulfide and anhydrous tetramethylam-monium fluoride opens a convenient route to perfluoro[3-(methylsulfanyl)bcnzonitrile].53 The reaction was carried out with a 10 17 2 ratio of perfluorobenzonitrile/ carbon disulfide/tetra-methylammonium fluoride in dimethylformamide under exclusion of water at 25 C over three days, to yield 18 % of perfluoro[3-(methylsulfanyl)benzonitrile] bp 202-204 C (note the meta-rather than the expected /wra-product). The reaction is explained by assuming the intermediate formation of the dithiofluoroformic acid anion which reacts with the perfluorobenzonitrile. The primary product of this reaction could not be isolated, because it is readily fluorinated to the (trifluoromethylsulfanyl)-substituted product. 

In support of the intermediate formation of the acetate radical from N-nitrosoacetanilide is the evolution of carbon dioxide during the reaction. Moreover, metals such as copper, zinc, lead, antimony, and iron are attacked when N-nitrosoacetanilide is allowed to decompose in a non-polar solvent such as carbon disulfide in the presence of the metals, a behavior similar to that of metals in contact with active free radicals in the Paneth test. 

A theoretical study of the mechanism of ruthenium-catalyzed formation of pyran-2-one and the corresponding sulfur and selenium analogues 8 from acetylene and CX2 (X = O, S, Se) has been reported (Equation 3) <2004NJC153>. This cyclotrimerization reaction has been experimentally carried out using carbon disulfide as a substrate <2002JA28>. The proposed mechanism involves formation of a bicyclic metal carbene intermediate. Formation of this intermediate seems to be particularly unfavorable energetically in the case of carbon diselenide. 

The reaction of 2-aminobenzonitriles 12 (X = CH = CH Y = CH) with carbon disulfide in pyridine solution constitutes a convenient, one-step synthesis of quinazoline-2,4(l//,37/)-dithiones 14. The reaction is also generally applicable to heterocyelic 2-aminonitriles 12 (X = NH Y = N) which afford fused pyrimidinedithiones 14. The reaction proceeds via the intermediate formation of 13 which rearranges rapidly and irreversibly by a base-catalyzed ring-opening-ring-closure sequence to give the observed product. ... 

Presumably this reaction proceeds via an allylic carbocation intermediate 301 formed by Lewis acid-initiated C-S cleavage, then ring closure to a new carbocation 302 stabilized by the silyl group. As illustrated in Scheme 55, the subsequent steps, leading to final product 300, involve disulfide bond formation, double-bond shift, and hydride migration. 

Phosphorylation of alcohols and amines forming mixed esters of phosphoric acid and phosphorami-dates, respectively, is effected by triphenylphosphine and 2,2 -dipyridyl disulfide. The reaction passes through a triphenylphosphonium phosphate of type (68 equation 44) as an active intermediate. Formation of an intemucleotide linkage can be achieved by this method. °° Dimerization of monoesters of phosphoric acid producing dialkyl pyrophosphates is achieved using tributylphosphine and dibenzoyl-ethylene or p-quinonedibenzimide (equation 45). A phosphonium phosphate is the active intermediate of this reaction. ... 

Young and Wood (389) did not isolate the intermediate benzoyl dithiocarbazic acids (LXXXII) which readily loose hydrogen sulfide on warming to yield the 5 substituted zl4-l,3,4-oxadiazoIine-2-thiones (LXXXIII). These authors suggested another reaction mechanism involving the intermediate formation of a xanthate type salt (LXXXVI) through nucleophilic attack of the enol form of the carboxylic acid hydrazide (LXXXIb) on carbon disulfide. 

Both FAD and NAD are electron-accepting coenzymes. Why is FAD used in some reactions and NAD in others Their unique structural features enable FAD and NAD to act as electron acceptors in different types of reactions, and play different physiological roles in the cell. FAD is able to accept single electrons (El ), and forms a half-reduced single electron intermediate (Fig. 20.4). It thus participates in reactions in which single electrons are transferred independently from two different atoms, which occurs in double bond formation (e.g., succinate to fumarate) and disulfide bond formation (e.g., lipoate to lipoate disulfide in the a-ketoglutarate... 

Thiol-disulfide isomerization. Disulfide bond formation between Cys residues takes place commonly in the ER during protein biosynthesis. The thiol-disulfide isomerization can occur by either chemical exchange reaction or enzymatic reaction catalyzed by protein disulfide isomerase via mixed disulfide intermediate (protein-S-SG). 

Yanagisawa and Ando [38] reported an elegant [2,3] sigmatropic rearrangement of 7a-benzoylamino-3-methylenecepham sulfoxide (99) into the sulfenate intermediate (100), which could be trapped with mercaptans to give the disulfides (101). Formation of the epi-oxazoline derivative (47a) by treatment with chlorine was followed by intramolecular etherification with boron trifluoride to obtain 3-methylene-1-oxacepham (48) with 10% overall yield from (99). 

Oae and Numata proposed intermediate formation of a S-S dication 5 in order to explain migration of the oxygen occurred when 4 was treated with concentrated sulfuric acid. Similarly, Ruffato and Miotti proposed formation of a disulfonium dication as a result of intramolecular interaction during the oxygen atom transfer from arylmethylsulfoxide to dialkyl disulfide. In 1974, Simonet et al suggested transient formation of an extremely unstable S-S dication 7 (Scheme 3) during electrochemical oxidation of thioketals 6 to afford disulfides 9 and carbonyl compounds 8 after hydrolysis. 

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