Hydrazines from hydrazones

Phenylhydrazine hydrogen chloride Carbalkoxy-hydrazines from -hydrazones Cleavage... 

Synthesis of hydrazines from hydrazones Addition of organometallic compounds to carbon-nitrogen double bonds... 

Of the further functional derivatives of cyclopropenones in the diphenyl series, the oxime115,121) and several hydrazones115) (e.g. 158/159), and a2ines (e.g. 760U5)), are easily available from the ethoxy cation 75 and hydroxylamine, hydrazines, and hydrazones, respectively. Sometimes oximation of cyclopropenones produces unexpected results (see later and Ref.42 ). 

The formation of derivatives of 2,3,6,8-tetraazabicyclo-[3.2.1]3-octene (425) arises from an intramolecular nucleophilic addition to the nitrone group of hydra-zone (424). Compound (424) was prepared by reaction of 2-acyl-3-imidazoline-3-oxides (423) with hydrazine. From the cis- and frans-derivatives (424), exo- and enr/o-isomers (425) were obtained (Scheme 2.197). The reaction of intramolecular cyclization does not occur in cases with monosubstituted hydrazones (316). 

Hydrazones are readily prepared from a variety of ketones with hydrazine or one of a number of substituted hydrazines. Some hydrazones may be converted into azo compounds by an isomerization procedure (see below). 

Platinum oxide has also been used for the preparation of monoalkyl- or monoaralkyl-hydrazines from the corresponding hydrazones.84,85 It is noted that the yields of hydrazines appear to have been improved considerably with use of ethanol-acetic acid as solvent,85 compared to the use of methanol.84... 

Phenyl-hydrazine Reaction.—Hydrazones.— The reaction with phenyl hydrazine has been given as one of the aldehyde or ketone reactions which prove the presence, in sugars, of the carbonyl group. The compounds resulting from this reaction are known as hydrazonesy or more specifically as phenyl hydrazones. With an aldo-hexose the reaction is as follows ... 

The hydrazone structure was preferred because of the ease with which S,S -dialkylation of N-aryl dithiocarbazates is known to take place and because acid hydrolysis of the product yields 1,3-dithio]sn-2-cne (CCXXIV) and the aryl hydrazine. The hydrazone (CCXXIII, R2=1 3=R.i=1 5 =H, Ri=CfiH5), independently prepared from 2-imino-1,3-dithiolane (CCX X. V ) 374 and phenylhydrazine 254), has the same melting point (94° C) and causes no lowering of the melting point when mixed with the product prepared from N-phenyl dithiocarbazate and 1,2-dibromoethane (m.p. 

Oxatriazines can be prepared by reaction of benzonitrile oxides, usually generated in situ from the corresponding benzohydroxamoyl chloride and triethylamine, with substituted hydrazines or hydrazones. Eor example, the nitrile oxide derived from 192 reacts with hydrazone 193 to yield oxatriazine 194 in good yield (Equation 16) <2005SOS(22)489>. 

A mixture of P-nitrostyrene, excess of nitromethane, and triethylamine allowed to stand at room temp, until reaction complete by t.l.c. (2-24 h), solvent (MeN02) replaced by ethanol, and stirred for 2 weeks with hydrazine hydrate at 80° 4-phenyl-pyrazole. Y 38%. F.e., also 2-step procedure via the intermediate 1,3-dinitro compds., s. F.e. Escribano et al.. Tetrahedron Letters 29, 6001-4 (1988) from hydrazones. 

---