With 2 different hetero atoms

Ihieno [2,3-b] thiophenes thiothiophthenes with 2 different hetero atoms... 

Indole contains a benzene ring fused with a pyrrole ring at C-2/C-3, and can be described as benzopyrrole. Indole is a ten tt electron aromatic system achieved from the delocalization of the lone pair of electrons on the nitrogen atom. Benzofuran and benzothiaphene are very similar to benzopyrrole (indole), with different hetero-atoms, oxygen and sulphur respectively. 

Selenazole is the selenium-containing compound in the series of heterocyclic 5-membered ring azoles with two different hetero atoms, of which the first two members are oxazole and thiazole. The numbering of the ring system is according to the scheme given (1). 

Unlike nickel Catalysts, palladium complexes do not catalyze the homo-cyclization reaction to give CDT or COD. The difference seems to be due to a different degree of hydride shift and atomic volume. With palladium catalysts, the hydride shift is easier, and hence linear oligomers are formed. The characteristic reaction catalyzed by palladium is the cocyclization of two moles of butadiene with one-hetero atom double bonds such as C=N and C=0 bonds to give six-membered rings with two vinyl groups (19) ... 

Numbering of the ring starts with the hetero atom and proceeds around the ring so as to give substituents (or other hetero atoms) the lowest numbered positions. When two or more different hetero atoms are present, oxygen takes precedence over sulfur and sulfur over nitrogen for the number one position. Examples follow to illustrate both the heterocycloalkane and the Hantzsch-Widman systems. Trivial names also are included. 

Treatment of the disodium salts of 7,8- and 7,9-B9H0CHE " (E = P or As) with Gel2 in refluxing benzene results in the formation of 1,2,3- and 1,2,7-GeBgHgCHE, icosahedral boranes containing three different hetero-atoms in the cage. The structures were deduced by the usual spectroscopic techniques, and that for the 1,2,3-isomer is shown in (45). The 1,2,7-isomer is thermally... 

Interconversion between two tautomeric structures can occur via discrete cationic or anionic intermediates (scheme 24, where T is an anion capable of reacting with a proton at a minimum of two distinct sites). Alternatively, interconversion can occur by simultaneous loss and gain of different protons (scheme 25, w here T has the same definition as in scheme 24). These mechanisms are well established for acyclic compounds, but they have been much less thoroughly investigated for heteroaromatic systems. The rate of interconversion of two tautomers is greatest when both of the alternative atoms to which the mobile proton can be attached arc hetero atoms, and isolation of the separate isomers is usually impossible in this case. If one of the alternative atoms involved in the tautomerization is carbon, the rate of interconversion is somewhat slower, but still fast. When both of the atoms in question are carbon, however, interconversion is... 

MSD provides molecular weight, fragmentation information and mass selectivity. Also, simultaneous GC-MS/MIP-AES has been described, using both a low-pressure and an atmospheric-pressure splitter [336]. The combination of MS and AED data sets provides the potential for application to a wide range of analytical problems, such as screening for the presence of hetero-atom-containing analytes (AED), identification and confirmation (MS) and quantification (MS, AED). On-line LVI-GC-AED/MS (dual detection) has been described with small (i.e. less than 0.5 s) differences in retention time of a compound with AED and MS detection [67], The dual-hyphenation set-up largely eliminates data-interpretation problems caused by small differences in retention time, or retention indices and is,... 

Interestingly, when the chloro analog was transmetallated and treated with 3-ethoxy cyclohexen-l-one, the expected enone (XI) was not observed, but an enone with a mass of 34 units greater than (XI) was noticed. It also indicated the enone carried the chloro analog. It was presumed that the hetero atoms in the heterocycle present in the starting material (VIII) had performed a directed metallated lithiation providing a different enone bearing the chloro moiety. 

The NMR and UV characteristics of 58a and b were shown to be consistent with a heavily buckled atropic frame and one whose hetero-atomic unit is directed syn to the methano bridge.60 It is also interesting to note in this connection that, whereas thia-annulene (58b) does differ rather significantly in some aspects of its NMR and UV spectra from... 

Hetero site reactivity The simplest difference between a cluster and a mononuclear complex is that the cluster can do two or more things where a mononuclear complex can do one. Simple as it is, this difference has hardly ever been verified other than in multiple ligand substitutions. One verification is hetero site reactivity, i.e., different modes of reaction at different sites on one and the same cluster. Two examples of this appear to exist. Different phosphine ligands substitute CO on different metal atoms in H2FeRu3(CO),3 depending on their size and basicity (210), and Ru2Co2 (CO), 3 reacts with H2 at the ruthenium atoms (cf. Section IV, A) and... 

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