Hydrazines addition reactions

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

In addition, several addition reactions have been reported for the iron complex [Fe(CNCH3)j] with hydrazine and with methylamine (99) the products (XVI) and (XVII), respectively, are described. A crystal structure study on the latter compound was carried out. 

Tricyclic antihistamines as a rule carry aliphatic nitrogen as a substituent on a side chain attached to the central ring the side chain nitrogen may be part of a heteroaromatic ring. Conjugate addition of p-chloroaniline (49) to the substituted vinylpyridine 50 gives the alkylated aniline 51. Treatment of that intermediate with nitrous acid leads to N-nitroso intermediate 52 which is then reduced to the hydrazine (53). Reaction of 53 with N-methyl-4-piperidone... 

The reaction of different substituted hydrazines (or hydroxylamines) with the a,/3-unsaturated ketones 210 gives pyrazolines 211 (or isoxazolines 212), as the result of a Michael addition reaction followed by an intramolecular Mannich reaction (Scheme 12) <2001FAR32>. 

The successful synthesis of 2-thienyl and substituted 2- and 3-thienyl-acetylenes in yields as high as 60-80% opened a wide variety of synthetic applications. Various addition reactions with carbonyl compounds or epoxides could be carried out with ease. Aliphatic as well as aromatic amine addition reactions, or condensation reactions with hydrazine or hydroxylamine could be easily performed. 

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. 

The reductive NO chemistry will cover some new developments on the electrophilic reactions of bound nitrosyl with different nucleophiles, particularly the nitrogen hydrides (hydrazine, hydroxylamine, ammonia, azide) and trioxodinitrate, along with new density functional theoretical (DFT) calculations which have allowed to better understand the detailed mechanistic features of these long-studied addition reactions, including the one with OH-. The redox chemistry of other molecules relevant to biochemistry, such as O2, H2O2 and the thiolates (SR-) will also be presented. 

Recent work describes the addition reactions of hydrazine and substituted derivatives to NP (62). The kinetic studies were done using UV-Vis absorption and mass spectrometric methods. Different stoichiometries were found, depending on the nucleophile. We can distinguish three different mechanistic paths, and these will be successively presented, with an effort to extract some common mechanistic features. 

Electrophilic addition reactions of tetravalent tellurium compounds have been reviewed.64 2-Naph-thyltellurium trichloride (ArTeCb) adds to alkenes in an anti stereospecific manner (equation 11), whereas tellurium tetrachloride gives mixtures of 2 1 adducts with both syn and anti addition.72 A one-pot alkene inversion procedure has been developed, based upon TeCU addition to alkenes followed by treatment of the (3-chloroalkyltellurium trichloride adduct with aqueous Na2S (Scheme 37).73 Tellurium compounds such as tellurinyl acetates, ArTe(0)0Ac, prepared in situ through reaction of tellurinic acid anhydrides with acetic acid, can be employed in oxytelluration and aminotelluration procedures (Schemes 38 and 39).74 In the oxytelluration reaction intermediate triacetates of the type RCH2Te(OAc)2Ph are reduced with hydrazine to the corresponding tellurides. 

Dihydropyrimidines 296 react very easily with water, forming 6-oxy derivatives 297 even during storage of 296 in solvents containing water and special catalysts [248]. There are examples of other addition reactions with water [326, 327, 328, 329, 330, 331], alcohols [82, 332], hydrazine and hydroxylamine [333]. 

Practically all linear 1,3-diketones13 7-142 give the corresponding pyrazoles with hydrazine104 143 and its derivatives.144-149 The reaction of aliphatic diketones should be moderated by dilution, cooling, or the addition of acid.137 Since pyrazole rings are stable, severe conditions may be used in their preparation where necessary. For details of the hydrazine/acetylacetone reaction see Wiley and Hexner.150 Evidently the reaction proceeds via the formation of the monohydrazone (11)151 which, when aryl-substituted, is less reactive and may be isolated.83,152-159 (However, see reference 159a.) It is not known if the monohydrazones are cyclic (12) or not, but they are... 

Although there is ample evidence for nucleophilic additions to benzyne la> and some other unstable angle strained cycloalkyne intermediates 15,27,31,205 207), only a few addition reactions to isolable angle strained cycloalkynes are known which can be classified as nucleophilic. Hydroxylamine and hydrazine add to (31) to yield the corresponding oxime and hydrazone, resp. 208). 

The adjacent nitrogen atoms in the furopyridazine ring systems suggest that reactions of hydrazines would be a viable synthetic approach. The furanone (190), readily obtained from a furanedione via a Wittig reaction, reacts with hydrazine in aqueous hydrochloric acid to produce compound (191)in 52% yield (Equation (66)) <88JOC5704>. Less acidic conditions lead to a six-membered ring via a Michael addition reaction. 

IV-Alkyl-substituted phthalimides 9 were easily transformed into mono-, di- or trisubslituted pyrazoles 10 via a one-pot addition/decyclization/cyclocondensation sequence <02JCS(P1)207>. 5-Silylpyrazoles can be prepared from condensation of silylalkynones with hydrazines <02T4975>. Reactions of acylated diethyl malonates with hydrazine monohydrochloride in ethanol afforded 3,4-disubstituted pyrazolin-5-ones <02T3639>. 

When the addition reactions were performed in the presence of (9-ethyl carbamate, 2-(0-elhylcarbamoylamino)-l-alkyl and 2-((9 -ethylcarbamoylamino)-alkyl phenyl tellurium oxides were formed. The tellurium oxides were once again not isolated but reduced with hydrazine hydrate to the corresponding alkyl phenyl telluriums4. 

In the classic carbohydrate chemistry addition reactions of carbonyl groups served as valuable tools for sturctural studies of carbohydrates. For example, hydroxyl amine, hydrazine, and phenyl hydrazine react with carbonyl groups to yield oximes and hydrazones. In the presence of an excess... 

With more vigorously reacting nucleophiles, such as malononitrile, hy-droxylamine, and hydrazines, the 1,2-addition reactions are often followed by ring opening, as described in Section III,C. 

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