Diacylhydrazine derivatives

Our aim was to synthesize a series of different oxadiazole monomers which are functionalized for the preparation of polymers. Scheme 2.2 shows the synthesis of the monomeric 1,3,4-oxadiazoles. The oxadiazole moiety is formed by a cyclisation reaction of the diacylhydrazine derivatives 8 with phosphorous oxychloride. The unsymmetrical bishydra-zides 8 are prepared by treatment of benzoyl chlorides 6 with the appropriate monohydra-zides 7. The last reaction step is an esterification with 4-(5-hexenyloxy)benzoyl chloride. The esterification reaction is essential in this case because of two reasons. First the rod-like... 

Diacylhydrazines (32) on heating with a primary amine undergo cyclization to the 1,2,4-triazole derivative (38). It is assumed that the amidrazone (37) is an intermediate in the reaction. Most practical syntheses of 1,2,4-triazoles now utilize an amidrazone or a derivative of this alicyclic intermediate containing three nitrogen atoms, and these variations are discussed in Chapter 4.12. 

The pyrrolo[l,2-4][l,2,4]triazinone skeleton 76 was also accessible in quantitative yield through a triflic acid-catalyzed heterocyclization of trisilylated diacylhydrazines 75 derived from pyroglutamic acid (Equation 10) <1996JHC1073>. 

The malonate derivative (93) reacted with acylhydrazine (94) to give a mixture of diacylhydrazine monoenamine (95) and oxadiazole (88c), (Scheme 6) which was also formed from (95) on heating <88LA909). 

Reaction of 232 with 4-substituted l,3-oxazol-5(4/7)-one 247 led to diacylhydrazines 248 or to imidazole derivatives 249 depending on the reaction temperature (Scheme 24). l,2,4-Triazole-3-thione 250 was obtained by a two-step sequence from 232 with phenyl isothiocyanate and subsequent base-catalyzed cyclization of thiosemicarbazide 251. The effects of hydrazones 241-246 on inhibition of photosynthetic electron transport in spinach chloroplasts and chlorophyll content in the antialgal suspensions of Chlorella vulgaris were investigated <2005CEC622>. 

Acetamide derivatives of dibenzoxazepine 113 were prepared and amidated with different alkyl and aralkyl side chains in order to function as a potential surrogate for the diacylhydrazine group of SC-51089, a potent PGE2 antagonist (Figure 15) <1996JME609>. 

Substituted acylhydrazones (95), formally derivatives of 1,2-diacylhydrazines (75), also cyclize to oxadiazoles (76), with loss of HX. Imidol ethers (95a R2 = H), prepared from acylhydrazines R1CONHNH2 and ortho esters HC(OR)3, cyclize on heating to monosub-stituted oxadiazoles (76 R1 = H). This reaction is an important synthesis of monosubstituted... 

Diacylhydrazine insecticides are all derivatives of hydrazine (H2N-NH2). The following compounds are essentially nontoxic to mammals, their oral LD50 s in rats being >5000 mg/kg. 

Several publications and patents describe the preparation of 2,5-di-aryl-l,3,4-thiadiazoles by treatment of mono- or 1,2-diacylhydrazines with phosphorus pentasulfide or by oxidation of thiobenzhydrazones of aromatic aldehydes with ferric chloride. The 2,5-bis-4-pyridyl derivative was prepared by reaction between thioisonicotinamide and hydrazine. Hydroxydithiobenzoates, useful as thioacylating agents in the method of Jensen, are readily available by a new synthetic... 

There are several recent methods for the reduction of azobenzene to hydrazobenzene in near-quantitative yield. Samarium(II) iodide reduces azobenzene to hydrazobenzene rapidly at room temperature. Hydrogen telluride, generated in situ from aluminum telluride and water, reduces both azobenzene and azoxybenzene to hydrazobenzene a mixture of phenyllithium and tellurium powder has been used to reduce azobenzene. A complex of the coenzyme dihydrolipoamide and iron(II) is also effective for the reduction of azo- and azoxy-benzene to hydrazobenzene the reduction probably involves coordination of the azobenzene to iron(II) as shown in structure (1). Electrochemical reduction has been used to prepare a number of hydrazobenzenes from the corresponding azobenzenes. In the presence of an acylating agent a diacylhydrazine (e.g. the pyridazinedione derivative 2) can be isolated from the electrochemical reduction of azobenzene. 

Phosphazenes, derived from hydrazines and acetylenic esters, were employed in the regioselective synthesis of 5-pyrazolones and pyrazoles <1999T14451>. Reactions of isocyanides 637 and dialkyl acetylenedicarboxylates 638 in the presence of 1,2-diacylhydrazines 639 led to highly functionalized pyrazolines 640 (Equation 133) <2005TL6545>. 

Under anhydrous conditions 3,6-diphenyl-1,4-dihydro-1,2,4,5-tetrazine isomerizes to the 4-amino-1,2,4-triazole derivative (326). Hydrolysis under the influence of acids or bases transforms the 1,4-dihydro-1,2,4,5-tetrazine system to diacylhydrazines (329), carboxylic acids (330), and hydrazine, 1,3,4-oxadiazoles (328), or 1,2,4-triazoles (327) depending on the reaction conditions <78HC(33)1077>. 

More recently, the synthesis of 1,3,4-oxadiazoles 73, including fluorinated derivatives, from 1,2-diacylhydrazines was reported by using [Et2NSF2]BF4 as a convenient cyclodehydration agent (Scheme 21) [40]. 

Peroxyacetic acid is a better oxidizing agent for hydrazine derivatives than yellow mercuric oxide and can be used in solvents in which the reactants are sufficiently soluble. F. e. and reactions such as cleavage of semicarbazones, formation of diacylhydrazines from carboxylic acid hydrazides, s. L. Horner and H. Fernekess, B. 9A, 712 (1961) s. a. Synth. Meth. 16, 58, 254, 359. 

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