Semicarbazide, 1-Phenyl

The percentage of dicoordinated phosphorus compound present depends equally on the substituent R, on the solvent and on the temperature. It has been possible to prepare these oligomers from monosubstituted aliphatic or aromatic diamines, from amidrazones, from semicarbazides, from substituted thiosemicarbazides, from 2-aminophenol, from 2-aminothiophenol and even from the monoimines of orthophenylediamine (Table I). It seems that these oligomers are generally the thermodynamic products of the reaction, except perhaps for the amidrazones, and the 1-phenyl semicarbazide in which case they would be kinetic products (the thermodynamic products being the triazaphospholes). 

To achieve a reasonable sensitivity in the relevant range, the first reaction equivalents are captured by means of phenylsemicarbazide and p-methoxy-phenyl semicarbazide. 

Resolution 3t3-Acetoxy-A. etienic add. T-Acid from a tetranitrofluorenone and an optically active hydroxylamine. i><—>Butane-2,3-diol. L.(+)-Butane-2,3-dithiol. (By crystallization Silver acetate). 10-Camphorsulfonic acid. 10-Camphorsulfonyl chloride. 4-(4-Carboxy-phenyl) semicarbazide. Complex from ethylene, platinous chloride, and (- -)-l-phenyi-2-aminopropane. Debydroataetylamine. Diisopinocampheylborane. Di-p-toluoyl-o-tartrate. d- and /-u-Phenylethylamiiie. L-Pyrrolidonecarboxylic add. a-(2,4,S,7-Tetianitro-9-fluorenyl-ideneaminooxy)-propionic acids. 

Phenyl semicarbazide may be converted to phenyl azide in 30% yield. Further examples are included in the tables at the end of the chapter. 

If there is no phenyl substituent in the 3-position the amination ability decreases. The acyloxaziridine (104) yields only 11% of a semicarbazide derivative with piperidine. In the presence of strong bases an intramolecular amination competes. Compound (104) reacts with methoxide within a couple of seconds to give phenylhydrazine carboxylic ester (106), and with cyclohexylamine to give the substituted semicarbazide (107). A diaziridinone (105) is assumed to be the common intermediate, formed by an intramolecular reaction from deprotonated (104) (67CB2600). 

Phenyl isocyanate, with ethyl hydrazinecarboxylate to give 4-phenyl-1-carbethoxy-semicarbazide, 51, 122 Phenylmagnesium bromide, o-... 

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,... 

G.A. Lyles, C.M.S. Marshall, I.A. McDonald, P. Bey, M.G. Palfreyman, Inhibition of rat aorta semicarbazide-sensitive amine oxidase by 2-phenyl-3-haloallylamines and related compounds, Biochem. Pharmacol 36 (1987) 2847-2853. 

Spiro and Fabra (72MII) reinvestigated the reaction of semicarbazide with benzoylacetonitrile. The authors showed that the product that melted at 170°C, previously reported to be 5-phenylpyrazole-l-carboxamide (52G373), is 3-phenyl-3-ketopropionitrilesemicarbazone. The other product (m.p. 278°C), for which no structure was proposed, is 7-amino-2,5-diphenylpyrazolo[ 1,5-a]pyrimidine (85). 

The preparation of phenylsemicarbazide from aniline and hydrazine hydrate is one of the earliest reports of this method [4]. Some more recent examples are reported for the preparation of 2-p-cymyl-4-semicarbazide [5], phenyl-thiosemicarbazides [6], and 1-isonicotinylsemicarbazide [7]. 

The stereoselective synthesis of both trans-88 and cis isomers 89 of pyrazo-lines was reported in [62] (Scheme 2.22). The configuration of the reaction products depends on the conditions of the cyclocondensation involving unsaturated ketones 87 and methyl(phenyl)hydrazines or (thio)semicarbazide. In boiling pyridine the treatment yields only raws-pyrazolines, while reaction in ethanol with catalytic amounts of hydrochloric acid leads mainly to the cis... 

H-l,2,4-Triazot 5-Hydrazino-3-[3-(bzw. 4)-hydroxy-phenyl]- EI6a, 787 (Semicarbazid-Spalt.)... 

Semicarbazid l-(4-Brom-phenyl)-4-methyl-4-(methyl-aminocarbo-nyl)- E4. 1041 (Cl -> NR2)... 

---