Heterocyclic compounds heteroatomic

Functional groups Acyclic compounds Isocyclic compounds Heterocyclic compounds Heteroatom type and number (n) ... 

Sulfur containing heterocycles are also common Compounds m which sulfur is the heteroatom m three four five and six membered rings as well as larger rings are all well known Two interesting heterocyclic compounds that contain sulfur-sulfur bonds are hpoic acid and lenthiomne... 

Substances that contain one or more atoms other than carbon as part of a nng are called heterocyclic compounds Rings m which the heteroatom IS oxygen nitrogen or sulfur rank as both the most common and the most important... 

HETCOR (Section 13 19) A 2D NMR technique that correlates the H chemical shift of a proton to the chemical shift of the carbon to which it is attached HETCOR stands for heteronuclear chemical shift correlation Heteroatom (Section 1 7) An atom in an organic molecule that IS neither carbon nor hydrogen Heterocyclic compound (Section 3 15) Cyclic compound in which one or more of the atoms in the nng are elements other than carbon Heterocyclic compounds may or may not be aromatic... 

Details of bond lengths and bond angles for all the X-ray structures of heterocyclic compounds through 1970 are listed in Physical Methods in Heterocyclic Chemistry , volume 5. This compilation contains many examples for five-membered rings containing two heteroatoms, particularly pyrazoles, imidazoles, Isoxazoles, oxazoles, isothlazoles, thlazoles, 1,2-dlthloles and 1,3-dlthloles. Further examples of more recent measurements on these heterocyclic compounds can be found in the monograph chapters. 

The NMR spectra of heterocyclic compounds with seven or more ring members are as diverse as the shape, size and degree of unsaturation of the compounds. NMR is perhaps the most important physical method to ascertain the structure, especially the conformational statics and dynamics, of large heterocycles. Proton-proton coupling constants provide a wealth of data on the shape of the molecules, while chemical shift data, heteroatom-proton coupling constants and heteronuclear spectra give information of the electronic structure. Details are found in Chapters 5.16-5.22. Some data on seven-membered rings are included in Table 10. 

Heterocyclic compounds are normally classified according to the size of the heterocyclic ring and the nature and number of the heteroatoms, and the present work is organized on this basis. 

Part 1 (Volume 1) deals with (a) the nomenclature and the literature of heterocyclic compounds (Chapters 1.02 and 1.03), (b) various special topics (Chapters 1.04-1.15), and (c) rings containing less common heteroatoms (Chapters 1.16-1.22). 

Protons bound to heteroatoms in heterocyclic compounds are likely to be very mobile in solution and, where two or more heteroatoms are present in a structure, different isomers (tautomers) may be in equilibrium. As a case in point, consider the nucleotide bases (indicates the point of attachment to the sugar-phosphate backbone). 

Whereas the fulvalenes 1-6 are relatively unstable hydrocarbons and therefore largely of theoretical interest, their heteroatom analogs demand considerable attention in synthetic chemistry and material sciences. Tlie general principle of heterocyclic chemistry to relate heterocyclic compounds to carbocyclic ones was the driving force for the synthesis and their application to heteroful-valenes. Numerous heterocyclic derivatives iso-rr-electronic with, for example, heptafulvalene 3 were accessible in which pairs of carbon atoms linked by double bonds were replaced by heteroatoms capable of contributing two tt-electrons. By this principle, the well-known tetrathiafulvalene and its derivatives have been synthesized successfully (Scheme 2). 

Meerwein reactions can conveniently be used for syntheses of intermediates which can be cyclized to heterocyclic compounds, if an appropriate heteroatom substituent is present in the 2-position of the aniline derivative used for diazotization. For instance, Raucher and Koolpe (1983) described an elegant method for the synthesis of a variety of substituted indoles via the Meerwein arylation of vinyl acetate, vinyl bromide, or 2-acetoxy-l-alkenes with arenediazonium salts derived from 2-nitroani-line (Scheme 10-46). In the Meerwein reaction one obtains a mixture of the usual arylation/HCl-addition product (10.9) and the carbonyl compound 10.10, i. e., the product of hydrolysis of 10.9. For the subsequent reductive cyclization to the indole (10.11) the mixture of 10.9 and 10.10 can be treated with any of a variety of reducing agents, preferably Fe/HOAc. 

Another method of ascertaining the nature of the reacting species is to compare the reactivity of a heterocyclic compound with its derivative methylated at the heteroatom. Thus Katritzky and Ridgewell507 measured first-order rate coefficients (lO7 ) for reaction of 2,6-dimethoxypyridine, 2,4,6-trimethylpyridine and 1,2,4,6-tetramethylpyridinium sulphate with tritiated sulphuric acid over a range of temperatures (Table 145). 

Topics in Heterocyclic Chemistry presents critical accounts of heterocyclic compounds (cyclic compounds containing at least one heteroatom other than carbon in the ring) ranging from three members to supramolecules. More than half of the more than 10000 compounds hsted in Chemical Abstracts are hete-rocychc compounds. The branch of chemistry deahng with these heterocyclic compounds is called heterocyclic chemistry, which is the largest branch of chemistry and as such the chemical hterature appearing every year as research papers and review articles is vast and can not be covered in a single volume. 

Narasimhan, N. S., Mali, R. S. Heteroatom Directed Aromatic Lithiation Reactions for the Synthesis of Condensed Heterocyclic Compounds, 138, 63-147 (1986). 

Chemical properties and structure of heterocycles containing P—C—O and P—C—N fragments are determined by the interaction between the heteroatoms. This interaction is most clearly pronounced in heterocyclic compounds also possessing an acceptor functional group (B(III), O—B(III), N—B(III), etc.). 

Heteroatom transfer in metallacyclopentadienes was first developed in the context of cobalt chemistry in the mid-1970s [27]. Cobaltacyclopentadienes were converted into various five-membered heterocyclic compounds such as pyrrole and thiophene, and into six-mem-bered heterocyclic compounds such as pyridine and pyridone derivatives. In the case of zirconacydopentadienes, the heteroatom compound must bear at least two halide substituents, since the Cp2Zr moiety is re-converted to the stable Cp2ZrX2. Indeed, this is the driving force behind the heteroatom transfer of zirconacydopentadienes. 

This article discusses the anodic synthesis of heterocyclic compounds that have appeared during the last decade. The mechanistic aspects involving intramolecular, intermolecular cyclizations and the homogeneous vs heterogeneous anodic oxidations were considered. This review deals with the recent advances in anodic oxidations in which heterocyclic compounds were synthesized through carbon-heteroatom and heteroatom-heteroatom bond formation. 

Since in the synthesis of heterocyclic compounds the ring closure usually involves the formation of the carbon-heteroatom bond, in the retrosynthetic analysis the first bond to be disconnected is the carbon-heteroatom bond (Cf. heuristic principle HP-8), either directly or after the pertinent (FGI or FGA) functional group manipulation. For instance, compound 17 -which is the starting material for Stork s synthesis of Aspidosperma alkaloids [30]- may be disconnected as shown in Scheme 6.11. 

The same "heuristic principles" which are applied to carbocyclic compounds also hold true for simple heterocyclic compounds containing one heteroatom. However, in the case of bridged heterocyclic molecules a modified strategic bond selection must be applied. Besides the strategic bonds which meet Corey s six rules, the bonds directly attached to nucleophilic heteroatoms -such as O, S and N-are also strategic Cf. heuristic principle HP-7), provided that they satisfy rules 2B, 4, 5 and 6. For instance, in compound 31a besides the five strategic bonds determined by rules 1-6 (cf. compound 26), the sixth darkened C-N bond in 31b is also a strategic bond. 

Hess s law phys chem The law that the evolved or absorbed heat in a chemical reaction is the same whether the reaction takes one step or several steps. Also known as the law of constant heat summation. hes-oz, 16 hetero- chem Prefix meaning different for example, a heterocyclic compound is one in which the ring is made of more than one kind of atom. hed-o-ro heteroatom org chem in an organic compound, any atom other than carbon or hydrogen. hed-3-ro,ad-3m ... 

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