With 2 different hetero

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. 

Ultraviolet spectra of 1,2,4-triazines substituted with different hetero substituents (amino, oxo, thioxo) are also published <83JOC1271,86JHC33,89RRC1321>. 

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). 

ChEs present several amphiphilic and soluble homo-and hetero-oligomeric molecular forms in tissues and body fluids, with different tissue distributions (Fig. 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) ... 

Park, P. J., Je, J. Y., Byun, H. G., Moon, S. H., and Kim, S. K. (2004b). Antimicrobial activity of hetero-chitosans and their oligosaccharides with different molecular weights. ]. Microbiol. Biotechnol. 14,317-323. 

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. 

An efficient, practical solid-phase synthesis of a variety of bis-hetero-cyclic compounds was developed starting from resin-bound orthogonally protected lysine (Fig. 10). Tetraamines 36 were synthesized by exhaustive reduction of resin-bound tetraamides 35. Cyclization with different commercially available bifunctional reagents such as cyanogen bromide, thio-carbonyldiimidazole, carbonyldiimidazole, and oxalyldiimidazole yielded the corresponding bis-heterocyclic compounds bis-cyclic guanidines 37,39 bis-cyclic thioureas 38, bis-cyclic ureas 39, and bis-diketopiperazines 40, respectively.40 Reduction of compounds 40 led to bis-piperazines 41. 

Fig. 5.5. Products of the multicomponent domino-Knoevenagel-hetero-Diels-Alder-hydrogenation sequence with a, fi- and y-amino aldehydes with different 1,3-dicarbonyl compounds.

Ozone acts as a very powerful oxidation agent and is capable of cleaving double bonds in a selective and fast way. Although this reagent can react with different organic groups (amines, sulfur compounds, phosphites, multiple and hetero multiple bonds, etc.), oxidation of olefins stays the most often encountered reaction, even on an industrial scale. 

The use of low bandgap polymers (ER < 1.8 eV) to extend the spectral sensitivity of bulk heterojunction solar cells is a real solution to this problem. These polymers can either substitute one of the two components in the bulk hetero junction (if their transport properties match) or they can be mixed into the blend. Such a three-component layer, comprising semiconductors with different bandgaps in a single layer, can be visualized as a variation of a tandem cell in which only the current and not the voltage can be added up. 

Further calculations were performed on 2,3-diaza-1,3-butadiene with different heterodienophiles such as ethene, formaldehyde and formaldimine showing the same exo oxygen or nitrogen lone pair preference [49] as well as on the nitro-soethene/ethene system [50]. Recently, ab initio studies have also been performed for the Lewis acid catalysed hetero Diels-Alder reaction of isoprene and sulfur dioxide by Sordo [51]. 

Numerous studies have dealt with different types of sulfur-containing hetero-dienophiles. Thus, hetero Diels-Alder reactions of N -sulfinyl dienophiles have been thoroughly studied by Weinreb et al. [454] the resulting cycloadducts represent useful and versatile intermediates in the synthesis of homoallylic amines [455] or pyrroles [456]. Further work using this type of S = N dienophiles... 

Heterobifunctional cross-linkers are modified with two hetero reactive groups that connect two molecules with different functionalities. In this respect, an oriented coupling between the modified surfaces and the reactant that has to be immobilized is guaranteed. 

Krishnaiah, A. and Narsaiah, B. 2002. Studies on inverse electron demand hetero Diels-Alder reaction of perfluoroalkyl 2(1H) pyridones with different dienophiles under microwave irradiation. Journal of Fluorine Chemistry, 113 133-37. 

The reducibility of the cations can be influenced by changing the substituents on the hetero atom. We used this approach to synthesize surfactants with different reduction potentials. The electrodeposition of latexes stabilized by these surfactants was then studied and the results correlated with reduction potential. 

With various nitriles, two different hetero dinuclear complexes with arrangement (73) are obtained (equation 35). The formation of the cyclometalated species (79) involves a hydrogen transfer from a Cp methyl group to the electrophilic carbon center of the nitrile in an intermediate fiilvene complex. Kinetic results indicate that a second molecule of nitrile catalyzes the conversion of this fiilvene intermediate into (80). ... 

The classical synthesis of quinoxalines involves the condensation of benzene-1,2-diamincs with different two-earbon synthons. The reaetion is also useful as a method of characterizing diketones. This reaction was first described by Korner and Hinsberg in 1884, and is still widely used for the synthesis of the parent system as well as for many derivatives bearing substituents in the hetero and/or in the benzenoid ring. 

The phosphonodithioformate (336) has been used as an interesting hetero-dienophile in the Diels-Alder reactions with different dienes. A selective radical desulfanylation of the cycloadducts (337) using BusSnH leads to new (3,6-dihydro-2H-thiopyran-2-yl) phosphonates (338)(Scheme 90). ... 

Carbo-cyclic Compounds.—Contrasted with the hetero-cyclic compounds, which we have just been discussing in a general way, we have other compounds whose constitution is also that of a closed ring or cycle, but this ring is composed of carbon groups only. To such we assign the names carbo-cyclic compounds or iso-cyclic compounds and they embrace not only hydrocarbons but also all of the different groups of derivatives which we have heretofore studied. 

Tables 3-11 are organized according to the a-heteroatom. Where there are two different hetero-substituted groups present in the carbanions, the listing in the tables is in accord with the priority sequence N, P, O, S, Se and halogen (as heteroatoms), COjR, CN, and metalloids. This takes no regard of the stabilizing effectiveness of the hetero-substituted groups present. Table 12 lists lithioformamides and -thioformamides.

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