Aliphatic heterocyclic compounds

The physical properties of a number of aliphatic ethers are collected in Table 111,60. Some related heterocyclic compounds are included in the Table. 

Thiophenealdehydes have been condensed with aliphatic aldehydes, methyl ketones,cyclic ketones, " benzyl cyanides,and aliphatic nitro compounds to the corresponding vinylthiophenes. By the use of potassium methylate, 2-thiophenealdehyde has been condensed with the reactive methyl groups of iV-heterocyclic compounds. Thiophenealdehydes have... 

Modern concepts have been extended to the chemistry of heterocyclic compounds more slowly than to the chemistry of aromatic and aliphatic systems, but efforts are now being made to classify and explain the properties and reactions of heterocyclic compounds in terms of these newer ideas (cf. reference 11). However, many of the most important heterocyclic compounds are potentially tautomeric, and elucidation of their tautomeric composition must precede a logical treatment of their properties. Further, many natural products such as the nucleic acids and alkaloids contain potentially tautomeric groups and information of this type is needed for a detailed explanation of th reactions which they undergo,... 

In a recent review of heterocyclic compounds no further mention is made of the three-membered ring structures for the condensation products from hydrazine and carbonyl compounds. However, the products obtained from azodicarbonyl derivatives with aliphatic diazo compounds were formulated as diaziridines [Eq. (1)]. Recent investi-... 

Silylthioaldehydes 103, reactive dienophiles formed in situ from acetals according to a general method, are directly trapped with dienes to afford sulfur-containing heterocyclic compounds in good yield (Equation 2.29). Silylthioaldehydes are quite reactive in comparison with the aliphatic ones [102] which are rather inert in the cycloaddition reactions. 

This condensation is completely analogous to that of ethyl diazoacetate, mentioned on p. 281, and, in general, azides and aliphatic diazo-compounds are strikingly similar in the manner in which they react with unsaturated substances like acetylenes, olefine derivatives, and hydrogen cyanide to yield heterocyclic compounds. 

Sawicki, E., S. P. McPherson, T. W. Stanley, J. Meeker, and W. C. Elbert. Quantitative composition of the urban atmosphere in terms of polynuclear aza heterocyclic compounds and aliphatic and polynuclear aromatic hydrocarbons. Int. J. Air Water Pollut. 9 515-524, 1%5. 

Kricheldorf and coworkers have found that some heterocyclic compounds containing two reactive bonds behave as bifunctional reactants in a ROP that proceeds by a step polymerization mechanism [Kricheldorf, 2000]. An example is the polymerization of 2,2-dibutyl-2-stanna-l,3-dioxepane with an aliphatic diacid chloride ... 

Diketene also is widely employed as a natural and synthetic fiber cross-linking agent, wood preservative and paper-sizing agent. Both it and /3-propiolactone have wide application as chemical intermediates. The synthetic applications of diketene for the synthesis of aromatic, heterocyclic and aliphatic compounds is exceptionally extensive (74ACR265). 

Unsaturated aliphatic compounds and heterocyclic compounds may also be metabolized via epoxide intermediates as shown in Figure 4.6 and chapter 5, Figure 14. Note that when the epoxide ring opens, the chlorine atom shifts to the adjacent carbon atom (Fig. 4.6). In the case of the furan ipomeanol and vinyl chloride, the epoxide intermediate is thought to be responsible for the toxicity (see below and chap. 7). Other examples of unsaturated aliphatic compounds, which may be toxic and are metabolized via epoxides, are diethylstilboestrol, allylisopropyl acetamide, which destroys cytochrome P-450, sedormid, and secobarbital. 

Figure 4.6 Metabolism of unsaturated aliphatic and heterocyclic compounds via epoxides.

Nitro derivatives of heterocyclic compounds are generally reduced similarly to carbocyclic analogs. However, whereas nontertiary aliphatic or ali-... 

Heterocyclic compounds (like carbocyclic compounds) can be divided into heteroaromatic and heteroalicyclic types. The chemistry of the heteroalicyclic compounds is in general similar to that of their aliphatic analogues, but that of heteroaromatic compounds involves additional principles. 

Steric effects can alter the reactivity of a heterocyclic compound as compared to its aliphatic analogue. For example, piperidine is less sterically hindered and more strongly nucleophilic than diethylamine. Conformations of these compounds are discussed elsewhere (Section 2.2.4.3). 

Conformational Analysis of Five- and Six-Membered Rings and Related Non-Bridged Systems (Saturated Heterocyclic) , F. G. Riddell, in Aliphatic, Alicyclic and Saturated Heterocyclic Compounds , ed. W. Parker, Royal Society of Chemistry, London, 1974, vol. 1, pt. 3, pp. 69-91. 

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