Phosphorus trichloride-Dimethylformamide

Amino-pyridazines and -pyridazinones react with monomethyl- or iV,A-dimethyl-formamide and other aliphatic amides in the presence of phosphorus trichloride, thionyl chloride, phosgene or benzenesuUonyl chloride to give mono- or di-alkylaminomethyl-eneamino derivatives. The same compounds can be prepared conveniently with A,iV-dimethylformamide dimethyl acetal in high yield (Scheme 50). 

Diisobutyl-3miethoxypyrazine 1,4-dioxide (107) with phosphorus trichloride in ethyl acetate at 40° gave 2,5-diisobutyl-3-methoxypyrazine (980). 2-Amino-5-[(/7-chlorophenoxy)methyl]-3-cyanopyrazine 1-oxide was deoxygenated with triethyl phosphite in dimethylformamide at 120° (1041). 

Chlorination (-Butyl hypochlorite. N-Chiorosuccinimide. Cupric chloride. Dibenzoyl peroxide. Dimethylformamide. Phosphorus pentachloride. Phosphorus trichloride. Selenium oxychloride. Sodium chlorate. Sulfuryl chloride. Tetra- -butylammonium iodotetrachloride. N,2,4,6-Tetrachloroacetanilide. Thionyl chloride. Trichloromethanesulfonyl chloride. Triphenylphosphine dichloride. 

Thiazole iV-oxides are easily deoxygenated to the parent thiazoles by a variety of reagents such as phosphorus trichloride <55JPJ12l>, sodium dithionite <85CPB618>, dimethylformamide at reflux <82JHC77>, or triethyl phosphite <91JMC108>. 

By analogy with the general synthesis of imidoyl chlorides it can be expected that carbamates and thiocarbamates undergo reaction with a variety of acid halides to afford 1-haloformimidates and 1-halothio-formimidates, respectively. For example, carbamates have been reacted with carbonyl chloride ( ), pyrocatecholphosphorus trichloride ( ), and phosphorus pentachloride ( ), and isocyanates were obtained. In view of the catalytic effect of N,N-dimethylformamide in the phosgenation of carbamates to isocyanates, the intermediacy of 1-chloroformimidates X is anticipated ( ). 

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