Nitrogen-containing heterocyclic compounds

FIGURE 5.5 Classes of nitrogen-containing heterocyclic volatiles formed via the Maillard reaction (a. pyrazine, b. methoxypyrazine, c. pyrrole, d. pyridine, e. pyrroline, f. pyrrolidine, g. pyrrolizine, and h. piperine). 

Hodge et al. [49] originally proposed a mechanism for the formation of pyrroles, which is also supported by Tressl et al. [50]. This basically is the participation of proline and hydroxy proline in the Strecker degradation to yield pyrroles. If the food system does not contain either proline or hydroxy proline, then a sugar of at least five or more carbons is required for pyrrole formation [51]. 

The mechanisms of pyridine formation are poorly characterized. Vemin and Parkanyi [12] have proposed three mechanisms. The first two mechanisms are dependent upon aldol condensations to yield unsaturated aldehydes with side groups. Reaction then with ammonia or an amino add and ring closure would yield a nitrogen-containing heterocyclic. The oxidation of this heterocyclic would result in the formation of a pyridine. The third pathway involves the reaction of dialdehydes with ammonia followed by dehydration to produce pyridines. 

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It is well known that in nitrogen-containing heterocyclic compounds the reactivity of alkyl groups is enhanced. In the thiazole series, alkyl groups in the 2-position are reactive towards carbonyl compounds and condensations may be realized. 

Their Esters with Nitrogen-Containing Heterocyclic Compounds... 

Dimethyl acetylenedicarboxylate gave first a similar adduct (2) which then added further molecules of furan yielding (3) and subsequently (4). Between 1931 and 1940 the reactions of acetylenedi-carboxylic acid and its dimethyl ester with a number of nitrogen containing heterocyclic compounds were examined, and structures were proposed for the products. Apart from an unpublished investigation of the products from pyridine and dimethyl acetylenedicar-... 

III. Reactions of Acetylenic Acids and Esters with Individual Nitrogen-Containing Heterocyclic Compounds... 

O. V. Kharitonova, A. B. Sheremetev, andT. S. Novikova, in The Vth All-Union Conference on Chemistry of Nitrogen Containing Heterocyclic Compounds., Oetober 22-25, 1991, Chernogolovka, USSR, 227 (in Russian). 

Reactions of Acetylenecarboxylic Acids and Their Esters with Nitrogen-Containing Heterocyclic Compounds R, M. Achbson... 

This method is the basis for synthesis of nitrogen-containing heterocyclic compounds when Z is a carbonyl-containing substituent.290... 

HMBC experiments are not limited to proton-carbon interaction. With suitable hardware, it is possible to acquire 1H-I5N spectra which can be extremely useful for confirming the identity of nitrogen-containing heterocyclic compounds. The sensitivity of this technique is very low, probably only about... 

Various schemes have been proposed to explain the production of nitrogen-containing heterocyclic compounds, such as pyrrolidines and piperidines, from proline. Nitrogen heterocyclic compounds are often potent flavouring chemicals. 

Nitrogen-containing heterocyclic compounds, including 1,2,3,4-tetrahydroqui-noline, piperidine, pyrrolidine and indoline, are also popular hydrogen donors for the reduction of aldehydes, alkenes, and alkynes [75, 76]. With piperidine as hydrogen donor, the highly reactive 1-piperidene intermediate undergoes trimer-ization or, in the presence of amines, an addition reaction [77]. Pyridine was not observed as a reaction product. 

The synthesis of oxygen- and nitrogen-containing heterocyclic compounds by anionic cyclization of unsaturated organolithium compounds has been reviewed recently. " Broka and Shen reported the first intramolecular reaction of an unstabilized a-amino-organolithium compound using reductive lithiation of an A,5-acetal derived from a homoaUylic secondary amine (Scheme 21). Just one example was reported treatment with lithium naphthalenide gave the pyrrolidine product, predominantly as the cis isomer. 

Some examples of nitrogen-containing heterocyclic compounds. 

Some examples of nitrogen-containing heterocyclic compounds containing more than one nitrogen atom. 

Y. Kikukawa, Nitrogen-containing heterocyclic compounds , Japanese Patent 60184063, 19 Sept. 1985 Chem. Abstr., 104, 68754 (1986). 

Pyrrole A nitrogen-containing, heterocyclic compound found at low concentrations in crude. Pyrrole can readily polymerize in the presence of light to form dark-brown compounds. Pyrrole derivatives, such as indole, have been identified as sources which can lead to darkening of fuel color and eventual deposit formation. 

The reaction of 113 with several Af-lithioamines was investigated and the results are summarized in Table 5. Af-Methylaniline, p-chloro-Af-methylaniline and Af-benzyl-p-anisidine gave 60-67% yield of the desired Af-cyclopropyl arylamines. Diphenylamine gave the desired product however, the yield was not satisfactory. Interestingly, dibenzy-lamine did not afford the desired product at all. This result indicated that the magnesium cyclopropylidene (113) only reacts with Af-lithio arylamines. The reaction of 113 with Af-lithio nitrogen-containing heterocyclic compounds was also studied. From the results shown in Table 5, the yields of the reaction are variable as a function of the heterocyclic compounds used. 

When pyrroles, triazoles and other nitrogen containing heterocyclic compounds react with dichlorocarbene, no addition to their carbon-carbon double bonds has been observed. In some cases the formation of cyclopropane adducts has been suspected however, alternate ways to explain the reaction products cannot be excluded [228]. 

PA (piperidine-2-carboxylic acid) is a nitrogen-containing heterocyclic compound with a molecular weight of 129.2. Its structure is shown in Fig. 2.4.1. 

The reagent F-Teda BF4 (6) is effective for the fluorination of nitrogen-containing heterocyclic compounds.107 Thus, 1-fluoroquinuclidinium (cf. preparation of compounds 3, vide supra), 1-fluoropyridinium (cf. Section 9.4.) and l-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate have been prepared in excellent yield by fluorination of quinuclidine, pyridine and 2,4,6-trimethylpyridine with F-Teda BF4 (6).107... 

Reactions of Acetylenecarboxylic Acids and Their Esters with Nitrogen-containing Heterocyclic Compounds R. M. Acheson, Adv. Heterocycl. Chem., 1963,1, 125-165. The Reactions of Diazomethane with Heterocyclic Compounds R. Gompper, Adv. Heterocycl. Chem., 1963, 2, 245-286. 

The composition of the carbonaceous species retained by sorption on sampling media has rarely been evaluated. Fung (59) reported that the carbonaceous materials retained by sorption on quartz-fiber filters were relatively polar organic compounds, including phthalate esters and nitrogen-containing heterocyclic compounds. Additional studies of this type would be very helpful. 

Methods of Introduction of Fluorine into Aromatic and Nitrogen-Containing Heterocyclic Compounds (Czech) Hradil, P, Radi, S Chem Listy M, 952-969 m... 

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