Carbonyl groups reaction with hydrazine

There are two methods for the introduction of a hydroxyalkyl group at position 5 of the pyrazol-3-one ring. Schmidt and Zimmer converted furanediones 258a-k into arylmethylenepyrazol-3-reaction with hydrazine hydrate or methylhydrazine (83Jmechanism proposed for the reaction involves nucleophilic attack of the hydrazine on the ketone carbonyl, followed by attack on the ester carbonyl and ring opening of the... 

Dicarbonyl compounds with a double bond in the 2,3-position condense with hydrazine to give pyridazines (e.g. 91 — 92). If one of the carbonyl groups in the starting material is part of a carboxyl group or a potential carboxyl group, then reactions with hydrazines or hydroxylamine lead to pyridazinones or 1,2-oxazinones (e.g. 93 — 94 Z = NH, NPh, O). Similarly a cyano group leads to an amino or imino product. 

Figure 46. The additional carbonyl group of rotaxane 57h can be used for further derivatiza-tion. Reaction with hydrazine 113 yields the E and Z isomers of the hydrazone rotaxane 114.

Various groups substituted between the two carbonyl groups of 1,3-ketones give highly substituted pyrazoles on reaction with hydrazine. Eor example, 4-alkoxypyrazoles 519 were synthesized from 3,5-heptadiones 518 with... 

Occasionally reactions with hydrazine must be performed with precautions. In order to avoid azine formation, excess of the reagent must be used, and if a cyclopropane bears two carbonyl groups, bi- and polycyclic products can result. ... 

In an unusual reaction, a furan derivative has been cyclized with hydrazine to give, after aerial oxidation in alkali, 6,9-dihydroxybenzo[ ]phthalazine-5,10-dione in excellent yield (Equation (40)). Normally furans need to be converted into unsaturated 1,4-dicarbonyl derivatives (bromine/ methanol, followed by hydrolysis) prior to reaction with hydrazine to give pyridazines, but in this case the carbonyl groups activate the furan to attack by hydrazine <93JHC1597>. 

Reductions. The use of hydrazine in the reduction of carbonyl compounds to their corresponding methylene groups via the Wolff-Kishner reduction has been covered extensively in the literature. The procedure involves the reaction of a carbonyl-containing compound with hydrazine at high temperatures in the presence of a base (usually Sodium Hydroxide or Potassium Hydroxide). The intermediate hydrazone is converted directly to the fully reduced species. A modification of the original conditions was used by Paquette in the synthesis of ( )-isocomene (eq 1 ). ... 

Scheme 4 shows in a general manner cyclocondensations considered to involve reaction mechanisms in which nucleophilic heteroatoms condense with electrophilic carbonyl groups in a 1,3-relationship to each other. The standard method of preparation of pyrazoles involves such condensations (see Chapter 4.04). With hydrazine itself the question of regiospecificity in the condensation does not occur. However, with a monosubstituted hydrazine such as methylhydrazine and 4,4-dimethoxybutan-2-one (105) two products were obtained the 1,3-dimethylpyrazole (106) and the 1,5-dimethylpyrazole (107). Although Scheme 4 represents this type of reaction as a relatively straightforward process, it is considerably more complex and an appreciable effort has been expended on its study (77BSF1163). Details of these reactions and the possible variations of the procedure may be found in Chapter 4.04. 

A recent paper by Singh et al. summarized the mechanism of the pyrazole formation via the Knorr reaction between diketones and monosubstituted hydrazines. The diketone is in equilibrium with its enolate forms 28a and 28b and NMR studies have shown the carbonyl group to react faster than its enolate forms.Computational studies were done to show that the product distribution ratio depended on the rates of dehydration of the 3,5-dihydroxy pyrazolidine intermediates of the two isomeric pathways for an unsymmetrical diketone 28. The affect of the hydrazine substituent R on the dehydration of the dihydroxy intermediates 19 and 22 was studied using semi-empirical calculations. ... 

MW irradiation conditions [80]. More recently, however, Varma and Kocevar s group have shown that a solvent-free and catalyst-free reaction of hydrazines with carbonyl compounds is possible upon MW irradiation (Scheme 6.24) [81]. Interestingly, the general reaction proceeds smoothly even for solid reactants and is completed below the melting points of the two reactants possibly via the formation of a eutectic. The reactions have been conducted in household MW oven and the control experiments are conducted concurrently in separate open beakers the reactions can be essentially followed by visual observation when a melt is obtained [82],... 

Simple amides are satisfactory protective groups only if the rest of the molecule can resist the vigorous acidic or alkaline hydrolysis necessary for their removal. For this reason, only amides that can be removed under mild conditions have been found useful as amino-protecting groups. Phthalimides are used to protect primary amino groups. The phthalimides can be cleaved by treatment with hydrazine. This reaction proceeds by initial nucleophilic addition at an imide carbonyl, followed by an intramolecular acyl transfer. 

Nitro compounds in presence of carbonyl group are selectively reduced to amines in the presence of Raney nickel catalyst. Hydrazine reduces nitrdes yielding hydrazones. Under controlled reaction conditions other functional groups, including nitroso and oxime, may be reduced. Many partially hydrogenated derivatives, such as azo-, hydrazo-, and azoxy compounds may be obtained by partial reduction with hydrazine. Reaction with chlorobenzene yields benzene. 

The diphenyl derivative 388, R = R = Ph, has an absorption band at 1495 cm S which has been assigned to the carbonyl group. This assignment could be questioned. The following chemical reactions of the compound 388, R = R = Ph, may be noted (a) Raney nickel desulfurization followed by oxidation with manganese dioxide yields dibenzyl ketone,(b) hydrazine yields 3,5-diphenyl-4-hydroxypyrazole (390), (c) phenylhydrazine yields PhCH2COCPh=NNHPh," (d)... 

There are no reports of nucleophilic attack at an unsubstituted carbon of tetrahydrooxazines, but the oxo derivatives are reactive toward nucleophiles. Nucleophilic substitutions are also known. The reactions of tetrahydrooxazin-3-ones are discussed first, followed by the less commonly used tetrahydrooxazin-2-ones. Both carbonyl groups of 206 react with hydrazines to form 207 (Equation 13) <1984EPP111809>. 

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