Phosphites reactions, carbon disulfide

Salts of dithiocarbamic acid can be prepared by the addition of primary or secondary amines to carbon disulfide. This reaction is similar to 16-9. Hydrogen sulfide can be eliminated from the product, directly or indirectly, to give isothiocyanates (RNCS). Isothiocyanates can be obtained directly by the reaction of primary amines and CS2 in pyridine in the presence of DCC. ° In the presence of diphenyl phosphite and pyridine, primary amines add to CO2 and to CS2 to give, respectively, symmetrically substituted ureas and thioureas ... 

The synthesis of 1,2,3-benzoselenadiazole (170) and its 4- and 5-methyl derivatives reported by Keimatsu and Satoda in 1935 constituted the first members of this ring system. [Eq. (43)]. No further work on this compound was reported until 1975, when the unsubstituted compound was used to make the two isomers of the dibenzodiselenadithiafulvalene (172) by the reaction of 170 with carbon disulfide and subsequent reaction of intermediate 171 with triethyl phosphite [Eq. (44)]. 

Considering that the chemical reactivity of carboxylic acids is similar to that of carbonic acids, as is observed in amide and ester formation, we have attempted the substitution of carbon dioxide for carboxylic acids in the coupling reaction with amines by using phosphites in pyridine or imidazole, and found that ureas are in fact produced in good yields (Eq. (4))6. Similarly, carbon disulfide reacts with amines to yield the corresponding thioureas (Eq. (5)). 

Displacement reactions with disulfides are a second major pathway to generate thiyl radicals. Formally, this constitutes a one-electron reduction of the disulfide. Homolytic sulfur-sulfur bond breakage by carbon-centered or phosphite radicals, for example, has been shown to lead to sulfides with mixed substitution and thiophosphates, respectively [17, 18], reactions (5) and (6) ... 

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