Hydrazones dimethyl, oxidation

Oxidative Couplings of Heterocyclic Hydrazones. This method has opened the way to the preparation of azo derivatives of diazo compounds unobtainable by other means, ie, heterocycHc compounds ia which the diazotizable amino group is conjugated with the heterocycHc nitrogen atom as ia 2- and 4-amiQopyridine, compounds which do not normally yield stable diazonium salts (38). The reaction occurs as illustrated by equation 7 for the iateraction of (A/-methylcarbostyryl)hydrazone [28219-37-6] and dimethyl aniline the overall process is oxidation. 

Basic Red 22 (134), which contains 1 part ia 7 of the yellowish red 1,4-dimethyl isomer, Basic Red 29 (135), and Basic Yellow 25 (136) are all examples of delocalized cationic azo dyes. Dyes of this type can also be synthesized by Hbnig s oxidative coupling reaction of heteroaromatic hydrazones with tertiary aromatic amines. 

To prepare fervenulin 4-oxides 12 or toxoflavine 4-oxides 146, it is convenient to use the reaction of l,3-dimethyl-2,4-dioxopyrimidin-6-yl hydrazone 147 or N-(3-methyl-2,4-dioxopyiimidin-6-yl) iV-methylhydrazone 148 with potassium nitrate in acetic acid [75CPB1885,76CPB338,76JCS(CC)658,82JHC1309,93CPB362]. Diethyl azodicarboxylate can be used instead of potassium nitrate [76JCS(P1 )713]. 

Chemical Name 1 (2H)-Phthalazinone-(1,3-dimethyl-2-butenylidene)-hydrazone Common Name Mesityl oxide (1-phthalazinyl) hydrezone... 

Considerable difficulties are often experienced in the preparation of basic dyes from quaternised heterocyclic diazo components. An alternative technique is to use an oxidative coupling procedure, in which a mixture of a hydrazone and a coupling component is treated with a mild oxidising agent, such as a hexacyanoferrate(III) [102] an azo compound is then produced as shown in Scheme 4.36 for the synthesis of Cl Basic Red 30 (4.100) [103]. Quaternisation of heterocyclic derivatives can lead to the formation of mixtures of isomers, as in the case of Cl Basic Red 22 (4.101). As well as the 2,4-dimethyl derivative shown, the product contains about 15% of the 1,4-dimethyl isomer [104]. 

The mixed hydrazones (667), prepared from diacetyl monobenzoyl hydrazone and arylhydrazines, undergo oxidative cyclization to 2-aryl-jV-benzoyl-4,5-dimethyl-l,2,3-triazol-l-ylimines (668) in 32-76% yield upon treatment with lead tetraacetate in acetonitrile (Scheme 132) <92JOC2252>. The cychzation of bishydrazones to 1,2,3-triazoles can also occur in acidic or basic media. For instance, the tetrahydrobenzo[ /]triazol-4-one (669) is prepared by the base-catalyzed cyclization of the corresponding a-hydrazono oxime (Equation (53)) <85HCA1748>. 3-Methyl-1,2-cyclohexanedione reacts... 

Zinc chloride-doped natural phosphate was shown to have catalytic behavior in the 1,3-dipolar cycloadditions of nucleoside acetylenes with azides to form triazolonucleosides <99SC1057>. A soluble polymer-supported 1,3-dipolar cycloaddition of carbohydrate-derived 1,2,3-triazoles has been reported <99H(51)1807>. 2-Styrylchromones and sodium azide were employed in the synthesis of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles <99H(51)481>. Lead(IV) acetate oxidation of mixed bis-aroyl hydrazones of biacetyl led to l-(a-aroyloxyarylideneamino)-3,5-dimethyl-l,2,3-triazoles <99H(51)599>. Reaction of 1-amino-3-methylbenzimidazolium chloride with lead(fV) acetate afforded l-methyl-l/f-benzotriazole <99BML961>. Hydrogenation reactions of some [l,2,3]triazolo[l,5-a]pyridines, [l,2,3]triazolo[l,5-a]quinolines, and [l,2,3]triazolo[l,5-a]isoquinolines were studied <99T12881>. 

Groups of reportedly photochromic systems which deserve further study include (a) disulfoxides (123,124), (b) hydrazones (125-129), (c) osazones (130-133), (d ) semicarbazones (134-143), (e) stilbene derivatives (144), (/) succinic anhydrides (145-148), and (g) various dyes (149,150). A number of individual compounds also remain unclassified as to their mechanism of photochromic activity. These include o-nitro-benzylidine isonicotinic acid hydrazide (151), 2,3-epoxy-2-ethyl-3-phenyl-1-indanone (152), p-diethyl- and p-dimethyl-aminophenyli-minocamphor (153), brucine salts of bromo- and chloro-nitromethionic acid (154), diphenacyldiphenylmethane (155,156), 2,4,4,6-tetraphenyl-1,4,-dihydropyridine (155,156), 2,4,4,6-3,5-dibenzoyltetrahydropyran (155,156), o-nitrobenzylidenedesoxybenzoin (157), p-nitrobenzylidene-desoxybenzoin (157), N-(3-pyridyl)sydnone (158,159), tetrabenzoyl-ethylene (160), and the oxidation product of 2,4,5-triphenylimidazole (161,162). 

Acetophenon 4-Nitro- -hydrazon Et4b, 508 (Umhydrazonierung) Benzofurazan-l-oxid 5-Dimethyl-amino- E8c, 783 (4-NR3-2-N3-l-N02-Ar/H ) Cyclopropan 1-Azidocarbonyl-l-Cyclopropylcarbonyl- E17b, 1568 (cycl.-En-ol-ester + HN3) Essigsaure Diazo- -(2-furfuryl-methyl-amid) E14b, 1196 (OR - NR2)... 

MyV-Dimethylhydrazones of aldehydes react with hydrogen peroxide in the presence of catalytic amounts of MTO to give the corresponding nitriles in high yield [19]. The reaction commences with the oxidation of the Af,A -dimethyl-hydrazone and presumably proceeds through an intermediate which can undergo a Cope-type elimination to yield the nitrile (eq. (8)) [3, 19 b]. 

In some methods, the final mixture is acidified slightly to stop the reaction, and the intensity of the yellow chro-mophore is measured at 400 nm. In stronger acid solution, the color becomes pink, with maximum absorbance at 540 nm, and both sensitivity and stability are improved. Other approaches to measurement of the H2O2 produced include the peroxide-mediated oxidative coupMng of 3-methyl 2-benzothia2olinone hydrazone (MBTH) with N,N-dimethyl-aniline (DMA) catalyzed by peroxidase or the oxidative coupHng of p-aminophenazone (PAP) to phenoi. Both procedures have been automated. The... 

Efforts to develop a y amino acid synthesis in which the oxidation state need not be adjusted after coupling led to the hypothesis that y hydrazonoesters may be com petent radical acceptors. Would the stereocontrol model be applicable in the presence of an additional Lewis basic ester function in the hydrazone. This question was addressed via prototypical Mn mediated photolytic conditions with InCla as the Lewis acid. Successful coupling was achieved between isopropyl iodide and a variety of y hydrazonoesters 52a S2d (Table 2.7, entries 1 4) bearing methyl, dimethyl, and benzyloxy substituents at the position (1 to the hydrazone (a to the ester). Consistently high diastereoselectivities and excellent yields (91 98%) of the isopropyl adducts S3a S3d indicated that the substitution patterns examined in this study had little effect on reaction selectivity and efficiency. 

Indolo-steroids have been obtained by -coupling of steroid dienamines with dia-zonium salts in dimethylformamide followed by Fischer-indole cyclization of the resulting hydrazone (Scheme 37). In methylene chloride the -coupled product 75 was obtained, cyclization of which gave indazoles 74 and 76 . The oxidative role of dimethyl sulphoxide in the formation of 76 was attributed to nucleophilic attack by the solvent on 75 leading to intermediates 77 and 78, with elimination of dimethyl sulphide (Scheme 38). 

Mit guten Ausbeutenlassen sich auch Dialkyl-hydrazone mit Palladium/Kohle bzw. Platin(IV)-oxid zu Trialkyl-hydrazinen hydrierenvgL 1 so erhalt man z. B. aus Formalde-hyd- bzw. Acetaldehyd-dimethylhydrazon iiber Pd/Kohle (25—3871 bar) 73% d.Th. Trimethyl-hydrazin bzw. 77% d.Th. 2,2-Dimethyl-l -athyl-hydrazin2. 

Enantioselective aldol reactions. Enders et ul. have reported a regiospecific and enantioselective aldol synthesis. The method involves conversion of a methyl ketone into the chiral hydrazone 2, a-metalation, reaction with a carbonyl compound, and silylation to form a doubly protected ketol 3. The chiral ketols 4 are obtained by oxidative hydrolysis with H2O2 (30%) at pH 7 or by sensitized photooxidation in THF followed by reduction with dimethyl sulfide. Optical yields are 30-60%. The absolute configuration of the ketols is not known at present. 

NCS is also regularly used for the direct oxidation of alcohols to ketones. The presence of Triethylamine serves to activate the reagent for rapid quantitative oxidation of catechols and hy-droquinones to o- and p-quinones, respectively, and for the oxidation of benzophenone hydrazone to diphenyldiazomethane. N-Chlorosuccininude—Dimethyl Sulfide is also used in the mild oxidation of alcohols, as well as in the conversion of allylic alcohols to allylic chlorides. 

Pentafluorobenzalddiyde reacts with bistrifluoromethyl nitroxide (see also p. 414) to give the amino-oxy-compound C6Fs CX>2-N(CF3)s, with the monohydrazide of cyclic trimeric phosphonitrile fluoride to give the hydrazone (117), and with ethyl acetoacetate and ammonia to give the expected dihydropyridine derivative (118). (Pfcntajauorophenyl)acetaldehyde is obtained in excellent yield from 2-(pentafluoropheny])ethanol and sodium dichromate in dimethyl sulphoxide the solvent may prevent further oxidation of the aldehyde. ... 

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