Amidine disulfides

N4S2C2 Amidine disulfides 5> m.-Di(thioformamidines) 15 Dithioureas Bithioureas 15 Hydrazonodisulfides... 

In the oxidative Eschenmoser sulfide contraction (Scheme 11), thioamide 59 is oxidized by benzoyl peroxide to give either a symmetrical disulfide or the O-benzoate of the thiolactam-S-oxide. In any event, the once-nucleophilic thioamide sulfur atom is now forced to adopt the role of electrophile a reactivity umpolung has, in effect, been achieved.13 The nucleophilic enamide 65 attacks the sulfur atom leading to the formation of sulfur-bridged intermediate 66. The action of a phosphine or a phosphite thiophile on the putative episulfide then gives vinylogous amidine 67. 

Amidines and cyclic amidines are also converted into 1,2,4-thiadiazoles by reaction with isothiocyanates, imino-sulfenyl chlorides, di- and trichloromethyl sulfenyl chlorides, and carbon disulfide in the presence of sulfur. Ureas, thioureas, guanidines, carbodiimides, and cyanimides react with chlorocarbonylsulfenyl chloride to produce 1,2,4-thiadiazol-5-one derivatives in another example of a type B synthesis <1996CHEC-II(4)307>. 

Amidines and amidoximes react with carbon disulfide and a mixture of carbon disulfide and sulfur to afford 5-mercapto-l,2,4-thiadiazole derivatives (see Section 5.08.9.3). 

Cyclic 1,2-diketones, 24 594 Cyclic acrolein acetals, 2 271 Cyclic amidine curing agents, 10 410 Cyclic amidines, 10 412 Cyclic (aromatic disulfide) oligomers, 23 712... 

Interest in the photochemistry of meso-ionic compounds is now developing, and an interesting result has been obtained by the photolysis of 5-amino-1,3-thiazolium salts (126, R = H). For example, irradiation of the salt 126, R = R = Ph, R = H, X = Cl, in aqueous solution yields the disulfide 130 (23%) and the keto amidine 131 (70%). It is proposed that this reaction involves a bicyclic intermediate (132). ... 

The condensation of 1,4-diamines with a variety of carboxylic acid derivatives, e.g. imidate esters, orthoformic esters, /V-ethoxycarbonylthioamides (77JOC2530), nitriles and ethoxyacetylene, produces the cyclic amidine linkage —N = C(R)NH— (67AHC(8)2l, p. 40). Cyclic ureas, —NHC(0)NH—, have been similarly produced using carbonyl chloride, A, A -carbonyldi imidazole, carbon monoxide, thiocarbonyl chloride or carbon disulfide (67AHC(8)21, p. 38). 

Scheme 28 outlines Eschenmoser s model corrin synthesis. The enamide (310) was treated with KCN to give (311), and this gave the thiolactam (312) when treated with phosphorus pentasulfide. Benzoyl peroxide oxidation yielded the disulfide (313), and in the presence of the enamide (310) this gave the bicyclo thio-bridged compound (314). Sulfur extrusion, by this time a standard procedure (Scheme 22), provided the vinylogous amidine (315)... 

Figure 135 DTBP reacts with amine-containing molecules to form charged amidine bonds. The internal disulfide group can be cleaved with DTT to release the conjugate.

Arretz, E., Lopez, F. Method for preparing organic disulfides and polysulfides from mercaptans and sulfur in the presence of heterogeneous styrene-divinylbenzene copolymer catalysts having pendant guanidine or amidine groups. 1996, WO 9721673. 

Amidines (282 R = H) also condense with carbon disulfide in the presence of sulfur to produce 5-mercapto-l,2,4-thiadiazoles (17) in reasonable yields, as indicated in Scheme 101 (68BRP1116198). A general method for the synthesis of 5-chloro-l,2,4-thiadiazoles (289 X = Cl) involves the reaction of amidines with trichloromethylsulfenyl chloride (288 X = Cl) in the presence of a base under mild conditions (Scheme 102) (65AHC(5)119). A variety of 3-substituted thiadiazoles (118) are obtained when dichloromethylsulfenyl chloride (288 X = H) is used in this reaction. 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

Many other functional groups are reduced by Sml. For example, sulfonyl halides are converted to disulfides. The reduction of nitro compounds by this reagent enables synthesis of 1,2-diamines based on a reaction sequence initiated by nitronate addition to aldimines, and in the presence of nitriles it furnishes amidines, and that of isothiocyanates in the presence of conjugated esters, the half thioamide derivatives of succinic esters. 

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