Benzil hydrazone

Benzil monohydrazone. Method 1. Boil a mixture of 26 g. of hydrazine sulphate, 55 g. of crystallised sodium acetate and 125 ml. of water for 5 minutes, cool to about 50°, and add 115 ml. of methyl alcohol. Filter off the precipitated sodium sulphate and wash with a little alcohol. Dissolve 25 g. of benzil (Section IV,126) in 40 ml. of hot methyl alcohol and add the above hydrazine solution, heated to 60°. Most of the benzil hydrazone separates immediately, but reflux for 30 minutes in order to increase the yield. Allow to cool, filter the hydrazone and wash it with a httle ether to remove the yellow colour. The yield is 25 g., m.p. 149-151° (decomp.). 

The known disuhstituted ketencs include dialkyl-ketcnes, diary lkctcncs. and ihe ester analogs. Rimcthylkelene may be made from u-bromoisobuiy-ryl bromide by reaction with zinc in boiling ether, Diphenylketene may be made similarly, but the usual way lo prepare it is to oxidize benzil hydrazone with yellow mercuric oxide to benzoylphenyldiuzomethnne which, on healing in benzene solution, decomposes inio Ihe ketene. 

A hot solution of 50 g. (0.24 mole) of benzil (Org. Syn. Coll. Vol. 1, 80) in 75 cc. of methyl alcohol is prepared, and the above solution, heated to 6o°, is added. Most of the benzil hydrazone separates immediately, but the yield is increased by refluxing a half hour. The hydrazone is filtered from the cold solution and washed with a little ether to remove the yellow color. The yield is 5°-5 g- (94 Per cent °f the theoretical amount), melting at 147-1510 with decomposition. 

Details for the preparation of benzil hydrazone are given in Organic Syntheses,901 and for preparation of benzophenone hydrazone by Barton et al.902... 

Colan The trivial name given to di-phenylethyne (diphenyl acetylene), CflHs C = C CeHs- Obtained as volatile colourless crystals, m.p. 6TC, by HgO oxidation of benzil bis-hydrazone. 

Benzil monohydrazone (610) and urea are reported to form 5,6-diphenyl-l,2,4-triazin-3-one (611) (71MI21903), and a-hydrazonocarboxylic acids (612) can be cyclized with imidates to l,2,4-triazin-5-ones (613) (74T3171). Both these reactions can also be treated as [2+2 + 2] syntheses, since the hydrazones (610) and (612) are prepared from the appropriate ketones and hydrazine. 

The nickel(n) complex of the 02N2 quadridentate (132) derived from benzil mono-hydrazone reacts with en or 1,2-pn at room temperatures, to produce complexes... 

Benzoylphenyldiazomethane was hydrogenated to 1,2-diphenylaminoethanol in ethyl acetate, but with uptake of 1 mol of hydrogen the intermediate benzil monohydrazone could be isolated in good yield (eq. 9.89). Hydrogenation of the hydrazone under the same conditions gave 1,2-diphenylaminoethanol in 60% yield. 

Diphenylacetylene has been prepared by the present method 1 by the action of sodium amide on monochlorostilbene 2 by the action of potassium amide on stilbene dichloride 3 by heating 1,1-diphenyl-2-chloroethane with sodium ethoxide in a sealed tube 4 and from benzil via the hydrazone.5... 

Many synthetic approaches are based on reactions with reactive methylene compounds and hydrazones, a reaction that was first introduced by Schmidt and Druey in 1954. Benzil or monohydrazones of benzil or related... 

Both N-N and N-C bond fission occurs on irradiation of the hydrazone derivatives (191). The photodegradation of the phenylhydrazone and the hydrazone of benzil have also been described. a-Ketoiminyl radicals are formed on irradiation of oximino ketones at low temperature. A study of the photochemical decomposition of sulfamic esters and their use as initiators of cross-linking of a melamine resin have been described. The bispyridinyl radical (192) is formed by one electron reduction of the corresponding pyridinium salts. The irradiation of this biradical at 77 K results in C-N bond fission with the formation of benzene-1,3-diyl. The predominant products from the irradiation (X,> 340 nm) of (193) in methanol were identified as A -hydroxy-2-pyridone and (194) from the fission of the C-O bond. Other products were 2-pyridone, (195) and (196) that arise from O-N bond fission. The reaction is to some extent substituent dependent and a detailed analysis of the reaction systems has identified an intramolecular exciplex as the key intermediate in the C-O bond heterolysis. 

Many hydrazone derivatives have been proposed as spectrophotometric reagents for Co, namely 2,2 -dipyridyl-2-pyridylhydrazone (e = 4.2-10 ), 2-furaldehyde-2-pyridylhydrazone [79], benzil-2-pyridylketone-2-pyridylhydrazone [80], and 2,2 -dipyridyl-2-benzothiazolyl-hydrazone [81]. Co was determined in the presence of Hg [82], and in the presence of Ni [83] by the derivative spectrophotometry using benzil-2-pyridylketo-2-quinolylhydrazone. 

In an unusual cyclization process, benzil monohydrazones heated in toluene form 4,5-diphenyl-imidazoles (>80%) rather than the expected pyrazoles. The way in which the N—N bond breaks and reorganizes is uncertain, but either a diaziridine or a diazetidine ylide intermediate may be involved. If it is the latter the 1,2-bond of imidazole is formed if the former it will be 1,5-bond formation <85TL1595,86BSB655>. Similarly, cyclization of phenacylethyleneketal hydrazones of benzaldehyde and ethanal yields both pyrazoles and imidazoles (Equation (62)) <86BSB1073>. 

Examples of substrates [23] with heteroatom double bonds (C = X) are presented in the rosette of Scheme 5. Here we feature the efficient denitrogenation of diazoalkanes, diazoquinones, the hydrazone of benzil, and benzophenone oxime into the respective carbonyl products [23]. On the other hand, the bis-oxime afforded furoxane, while the phosphorane led to methyl maleate on elimination of triphenylphosphine oxide [23], Thiones are oxidized to the corresponding S-oxides and the iodonium ylide yields the labile w c-trione [23],... 

Alternatively, the hydrazine unit may be introduced by the C2 fragment when the mono-hydrazone of benzil is used.255... 

A solution of benzil (10.5 g, 50 mmol) and guanidine-1,2-diamine hydroiodide (10.9 g, 50 mmol) in EtOH (100 mL) was refluxed for 5h and the dark brown solution concentrated to 30 mL. A pale brown solid (7.5 g mp 140-145 °C) was deposited when the concentrated solution was diluted with H20 (100 mL). The filtrate was made basic with NH4OH to afford benzil mono [((V-aminocarbamimidoyl)hydrazone] yield 5.0 g (36%) mp 96-98 °C (with resolidification and remelting at 171 -173 JC). 

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