Phosgene substitute diphosgene

Chlorination of methyi chloroformate and dimethyl carbonate affords useful phosgene substitutes chloromethyi chioroformate [I], trichioromethyl chloroformate [II] also called Diphosgene and bis(trichloromethyi) carbonate [III] known as Triphosgene [see scheme 33] ... 

Trichloromethyl CI3C-0-C-CI II 0 503-38-8 125/748 Phosgene substitute (also called diphosgene )... 

Pefurazoate can be synthesized [30] by transesterification of methyl 2-bromobutyrate with 4-pentenyl alcohol, substitution of the bromine by furfiiryl-amine, and imidazolylcarbonylation of the amine by phosgene or diphosgene and imidazole (Scheme 17.1). 

Trichloromethyl chloroformate (diphosgene) is used as a safe substitute for highly toxic phosgene gas. The latter is generated in situ by addition of catalytic amounts of tertiary amines or amides, or active carbon. Diphosgene also disproportionates to 2 equivalents of phosgene on heating above 250°C. 

The traditional use of phosgene in Scheme 4 can be avoided by substituting it with the less toxic triphosgene, which gives comparable yields of the M-car-boxyanhydrides. Diphosgene may also be used to form the NCA, but the reaction requires the use of charcoal and is not as reliable. Free amino acids have also been converted to their corresponding NCAs by the use of benzyl chloroforma-te with thionyl chloride. 

At the present time, one crucial question still remains what is the industrial value of Diphosgene and Triphosgene as liquid and solid substitutes for phosgene Are the two reagents really safer than phosgene ... 

Diphosgene has been widely used as a substitute compound for phosgene in different chemical synthesis... 

Suitable substituted triazole derivatives can be cyclized with phosgene or some of its substitutes (e.g., diphosgene, triphosgene, carbonyl diimidazole) to form the corresponding triazolotriazole derivatives. This approach can be demonstrated by reactions in Scheme 81 <77CB1691,84JOC1703>. 

Nucleophilic reactions of diphosgene highlight its reactivity as a tricoordinated carbonic acid derivative. Its phosgene equivalence can be rationalized in terms of the mechanistic scheme shown below (e.g. route a with a dialkylamine as HNu), whereby a mole of phosgene is released during the nucleophilic substitution. Several examples of route b have also been reported. From the reaction of diphosgene... 

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