Aldehydes reaction with ammonia

A pathway leading to the formation of pyridines by aldolization of aldehydes, reaction with ammonia and intramolecular cyclization has been proposed by Vernin (1981). Mottram (1991) explained the formation of 2-alkylpyridines by reaction of ammonia on dienals. 

Aldehydes by reaction with ammonia and cyanide ion (the Strecker synthesis)... 

An a-amino acid 3 can be prepared by treating aldehyde 1 with ammonia and hydrogen cyanide and a subsequent hydrolysis of the intermediate a-amino nitrile 2. This so-called Strecker synthesis - is a special case of the Mannich reaction-, it has found application for the synthesis of a-amino acids on an industrial scale. The reaction also works with ketones to yield a, a -disubstituted a-amino acids. 

Reaction with water to yield a carboxylic acid Reaction with an alcohol to yield an ester Reaction with ammonia or an amine to yield an amide Reaction with a hydride reducing agent to yield an aldehyde or an alcohol... 

Figure 1.98 Aldehydes may be transformed into primary amines by reaction with ammonia or a diamine in the presence of a reducing agent.

Electrophilic substitution of the ring hydrogen atom in 1,3,4-oxadiazoles is uncommon. In contrast, several reactions of electrophiles with C-linked substituents of 1,3,4-oxadiazole have been reported. 2,5-Diaryl-l,3,4-oxadiazoles are bromi-nated and nitrated on aryl substituents. Oxidation of 2,5-ditolyl-l,3,4-oxadiazole afforded the corresponding dialdehydes or dicarboxylic acids. 2-Methyl-5-phenyl-l,3,4-oxadiazole treated with butyllithium and then with isoamyl nitrite yielded the oxime of 5-phenyl-l,3,4-oxadiazol-2-carbaldehyde. 2-Chloromethyl-5-phenyl-l,3,4-oxadiazole under the action of sulfur and methyl iodide followed by amines affords the respective thioamides. 2-Chloromethyl-5-methyl-l,3,4-oxadia-zole and triethyl phosphite gave a product, which underwent a Wittig reation with aromatic aldehydes to form alkenes. Alkyl l,3,4-oxadiazole-2-carboxylates undergo typical reactions with ammonia, amines, and hydrazines to afford amides or hydrazides. It has been shown that 5-amino-l,3,4-oxadiazole-2-carboxylic acids and their esters decarboxylate. 

The two most important natural pentoses, 1 -arabinose and 1 -xylose, occur in nature as polymeric anhydrides, the so-called pentosans, viz. araban, the chief constituent of many vegetable gums (cherry gum, gum arabic, bran gum), and xylan, in wood. From these pentapolyoses there are produced by hydrolysis first the simple pentoses which are then converted by sufficiently strong acids into furfural. This aldehyde is thus also produced as a by-product in the saccharification of wood (cellulose) by dilute acids. Furfural, being a tertiary aldehyde, is very similar to benzaldehyde, and like the latter undergoes the acyloin reaction (furoin) and takes part in the Perkin synthesis. It also resembles benzaldehyde in its reaction with ammonia (p. 215). 

The conversion from aldehydes 3 into a-amino cyanides 4 can go either by reaction of aldehyde 3 with ammonia or ammonium chloride to yield an intermediate 6, followed by treatment of 6 with hydrogen cyanide or an alkali cyanide, or by treatment of the cyanohydrin 7, derived from reaction of aldehyde and cyanide, with ammonia or ammonium chloride (Scheme 3). 21 ... 

The original Strecker procedure is the reaction of an aldehyde with ammonia and then with hydrogen cyanide to form the a-amino nitrile. This intermediate may also be obtained by reacting the aldehyde cyanohydrin with ammonia, but a more convenient method is to treat the aldehyde in one step with ammonium chloride and sodium cyanide. The a-amino acid is obtained when the amino nitrile is hydrolysed under either acidic or basic conditions the former are usually preferred. The preparation of a-phenylglycine (R = Ph) from benzalde-hyde is typical of the general procedure (cognate preparation in Ept 5.181). 

Many 2-alkylpyridines were isolated and identified in roasted lamb fat (45). 2-Alkylpyridines were proposed to form from the corresponding unsaturated n-fatty aldehyde reacting with ammonia upon heat treatment. Ammonia, arising from glycine, can react with nonanal, arising from beef fat, produced 2-butylpyridine in a beef fat/glycine browning model system (6). The same phenomenon was observed in the formation of 2-pentylpyridine from 1-decanal. Maltol produced 2-ethyl-3-hydroxy-6-methylpyridine as a major product in a reaction with ammonia (12). 

A simple, stereocontrolled, and economical synthesis of m-2,4,5-triarylimidazolines 276 starts from the reaction of aromatic aldehydes 274 with ammonia to form 2,4-diazapentadienes 275. Deprotonation of 2,4-diazapentadienes 275 with a strong base or under thermal conditions results in formation of the transient 2,4-diazapentadienyl anion that cyclizes in a disrotatory fashion to furnish m-imidazolines 276 (Scheme 134) microwave irradiation facilitates the ring closure <1997TL8631, 2003S1236, 2005H(65)353, CHEC-III(4.02.9.1.3)295>. 

Simple saturated and olefinic aldehydes condense with ammonia to give alkylpytidines (Chichibabin), but the products are frequently complex mixtures from which pure compounds are separated with difficulty. An exception is the preparation of 5-ethyl-2-methylpyridine in 53% yield from paraldehyde and ammonium hydroxide. In an extensive study of the reaction, it has been pointed out that other single products can sometimes be obtained in fair yields by proper choice of reagents and conditions. ... 

Imprinted metal oxide two-dimensional films have also been prepared using a CVD technique developed by Kodakari et al. [14,15]. They demonstrated that molecular imprints of aromatic aldehydes could be prepared in monolayer films of silica deposited by CVD on Sn02 surfaces. Taking advantage of the specific adsorption of aldehydes to Sn02, templates such as benzaldehyde were dispersed and bound to the surface, followed by tetramethoxysilane deposition. The templates were removed from the surface by gas phase reaction with ammonia, converting the aldehydes to nitriles. Gas phase binding studies performed on the calcined films of imprinted and non-imprinted systems showed that size selective memory for the benzaldehyde template existed. 

The aldehyde was typically aromatic it gave the hydramide in its reaction with ammonia, and underwent the Cannizzaro reaction. CTM was phos-phorylated by PCI, in the presence of aluminium chloride to give... 

A two-step synthesis of 1,4-disubstituted imidazoles (8) from TOSMIC (1) plus an aldehyde, followed by reaction with ammonia or a primary amine, proceeds via a 4-tosyloxazoline (11). The reaction sequence could be classified as 1,2 and 1,5 bond formation, 1,5 bond formation, or transformation of another heterocycle. There are, however, analogies to the aldimine reactions, and so the process is detailed at this stage. Certainly the synthesis is carried out in two steps often with isolation of the oxazoline (see also Chapter 6). Heating (11) with a saturated solution of methanolic ammonia gives a 4-substituted imidazole with methanolic methylamine a 1,4-disubstituted product is isolated as a single regioisomer (Scheme 4.2.4). Some of the oxazolines cannot be isolated as they are unstable oils which have to be heated immediately with the amino compound [12]. Related is the synthesis of 2-carbamoyl-4-(2 -deoxy- 0-D-ribofuranosyl)imidazole [13]. 

C=N- Reaction with ammonia, primary amines, hydrazine, hydroxyl-amine, semicarbazide, Girard D reagent Ketones [206], aldehydes [206] irreducible under given conditions better developed waves with some reducible compounds simultaneous determination of pyridoxal and pyridoxal-5-phosphate [193], 17-ketosteroids [238],... 

Condensations. Alumina promotes the formation of a-hydroxyphosphonate esters from aromatic aldehydes and dialkyl phosphonates, and the adducts are converted to a-aminophosphonate esters on reaction with ammonia. A solvent-free synthesis of a-nitro ketones comprises mixing nitroalkanes, aldehydes, and neutral alumina and oxidizing the adducts with wet, alumina-supported CrOj (15 examples, 68-86%). The Knoevenagel reaction, the Michael addition of nitromethane to gcm-diactivated alkenes, and the formation of iminothiazolines from thioureas and a-halo ketones are readily effected with alumina under microwave irradiation. 

A route in which a synthon for such a dialdehyde is central depends on ortho lithiation of an aryl bromide for conversion to ortho bromoaryl aldehyde, then palladium-catalysed replacement of the halide with an alkyne, subsequent reaction with ammonia producing the isoquinoline. The sequence below shows how this type of approach can be used to produce naphthyridine mono-A-oxides by reaction of the alkynyl-aldehyde with hydroxylamine instead of ammonia. 

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