Semicarbazides reaction with, phosgene

The reaction of the N,N-dimethylamino semicarbazide derivative 1 with phosgene affords the chloroformamidine intermediate 2, which on treatment with sodium bicarbonate affords N-t-butyl-N -dimethylaminocarbodiimide 3, bp 150 °C in 64 % yield. ... 

Condensation of anthranilic acid with various ort/zo-esters and reaction of semicarbazides, gave 2-substituted benzoxazin-4-ones and also by the reaction of hydrazones with aryl-/alkyl-ureas and by salicylaldehyde or 2-hydroxyacetophenones with 4-aryl-/alkyl-semicarbazides. Hydrolysis of o-aminoesters and subsequent treatment with phosgene gave 40. Fused oxazine with bridge head nitrogen 41 and triazolo[3,4-Z>]thiazines 42 were also prepared . The 2,3-dihydrobenzoxazine 43, thiomorpholines 44 and phenothiazines 45 were prepared. ... 

A number of general methods for the synthesis of meso-ionic 1,2,4-triazol-3-ones are available. Sodium ethoxide-catalyzed cyclization of 1-benzoyl-l,4-diphenylsemicarbazide (201, R = R = R = Ph, X = O) yielded anhydro-3-hydroxy-1,4,5-triphenyl-1,2,4-triazolium hydroxide (200, R = R = R = Ph). A general route to meso-ionic 1,2,4-triazol-3-ones (200) is exemplified by the formation of the 1,4,5-triphenyl derivative (200, R = R = R = Ph) from A-amino-MA -diphenylbenzamidine (202, R = R = R = Ph) and phosgene. In contrast with this ready meso-ionic compound formation, the corresponding reaction of the iV-methylbenzamidine (202, R = Me, R = R = Ph) did not yield the meso-ionic 1,2,4-triazol-3-one (200, R = Me, R = R = Ph). The product was in fact 3,4-diphenyl-2-methyl-l,2,4-triazol-5-onium chloride (203), which on heating gave 3,4-diphenyl-1,2,4-triazol-5-one (204, R = Ph). The formation of the A-methyl derivative (200, R = Me, R = R = Ph, yield 79%) by heating the 7V-thiobenzoyl semicarbazide (201, R = Me, R = R = Ph, X = S) with potassium carbonate in methyl cyanide has been reported. Another synthesis of A-methyl derivatives (200, R = Me) involves methylation of 3-methyl-4-phenyl-l,2,4-triazol-5-one (204,... 

Oxatriazines. (1) Reaction of benzonitrile oxides with hydrazones (Equation 16) - this method gives 3-aryl derivatives (2) reaction of benzonitrile oxides with hydrazine carboxylates and cyclization (Scheme 33) (3) cyclic carbonylation of l,4-disubstituted-4-hydroxy-semicarbazides with (thio)phosgene (Scheme 41) - this method gives 3,6-dione-type derivatives. Methods (1) and (3) both appear quite general and high yielding, with precursors readily available. 

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