Benzo specials

PytomeUitic acid is a commercial product, and it forms a dianhydtide which has specialized commercial appHcations, primarily as an ingredient in the preparation of high temperature polymers. The lUPAC name of the dianhydtide is lJT,3JT-benzo(l,2- 4,5-/)difiitan-l,3,5,7-tettone. 

Except for several chapters in the comprehensive monograph on heterocyclic chemistry (84MI1) no special articles covering the recent past are available. This review is an attempt to discuss the literature up to Volume 117 (1992) covered by Chemical Abstracts together with some accessible papers published in 1993. Only isolable or spectroscopically identifiable thio-, seleno-, and teluropyrans without exocyclic double bonds (hetero-pyrones and heteropyranylidene derivatives) are considered. All benzo derivatives and their annulated heteroanalogs (spiroheteropyrans) are excluded. 

To evaluate the potential risk of Ebro river sediments, the concentrations detected were compared to actual legislation. The WFD does not specifically address sediment management [95]. In contrast to this, the Canadian sediment quality guidelines for the protection of aquatic life [96] provide data for different types of sediments and include 33 compounds, PAHs and DDTs among them. All the PAHs included in the Canadian guidelines are present above the limit, ranging from 3% of the samples for naphthalene to 90% for dibenzo(a,h)anthracene. Special attention has to be paid to benzo(a)pyrene and dibenzo(a,h)anthracene, considered... 

Concerning the transformation of substituents, a special note should be made on a series of ring-closure reactions carried out on the side chain of some [l,2,4]triazolo[4,3-r]benzo[l,2,3]triazines published by Moustafa <2001SC97>. The results are summarized in Scheme 18. This scheme shows that by transformation of the R group attached to the sulfur atom of derivative 97 a fairly large set of cyclic products - involving thiazolidone 97a, [l,2,4]triazole 97b, coumarone and its imine 97c and 97d, respectively, benzoxazylpyrane, 97e, thiophene 97f, and cyclopenta- or cyclohexa-fused protected pyrone 97g substituents - have been obtained. 

The use of metals for prearranging reaction centers as neighboring groups has a special value in the production of macrocycles (template effect). Although these ligands can be sometimes prepared directly, the addition of metal ion during the synthesis will often increase the yield, modify the stereochemical nature of the product, or even be essential in the buildup of the macrocycle. There have been few mechanistic studies of these processes. The alkali and alkaline-earth metal ions can promote the formation of benzo[18]crown-6 in methanol ... 

The special case of the fusion of a five-membered ring to the benzoheteropine ring occurs when the pyrrole or indole N1 and C2 atoms serve as fusion sites (Figure 2). The resultant benzopyrrolo[l,2-fl]azepines differ by the position of the fused benzo ring and are listed in the order of benzo[c]pyrrolo[l,2-fl]- (7), benzo[d]pyrrolo[l,2-fl]- (8), benzo[e]pyrrolo[l,2-fl]- (9) and benzo[/]pyrrolo[l,2-fl]-(10) azepines, respectively. 

Substituents at the C(4) and C(5) positions of 1,2,3-triazole and at the benzene ring of benzo-triazole can undergo normal functional transformations which are independent of the triazole ring. In addition, these substituents can undergo some specialized reactions, particularly the formation of triazolo fused bi- and tricyclic systems. 

All these special cases involve benzologs with an ortho quinonoid structure. But even this pattern is not universal, a deviation being 2-methylindazole (40), which quaternizes 2.2 times more slowly than its parent compound 1-methylpyrazole (37).122 Indeed, except for the molecules just considered and 1,2-benzisothiazole,122 benzo-fusion is rate retarding. Thus, 1,2-benzisoxazole (indoxazene, 39), reacts 3.2 times, and 1-methylindazole (39) 7.1 times, more slowly than their parent compounds.122 Fusing a benzene ring onto an azole where the heteroatoms are situated 1,3 leads to decreases in rate constants by factors of 5.0, 6.3, and 6.8, respectively, when X of 38 is NMe, S, and O.122 These factors are not much smaller than that obtained from a comparison of pyridine and quinoline reactivities.61,78,79... 

The concept of photostimulated phase separation can be applied to construct chemical-induced phase transition systems, which change the conformation reversibly in response to special chemicals. For the systems, host molecules are used as the receptor groups instead of photoisomerizable chromophores. Host molecules, such as crown ethers or cyclodextrins, are known to change the property by capturing guest chemicals in their cavity [16]. We employed benzo[l 8]crown-6 as the receptor molecule and incorporated it into the pendant groups of PNIPAM. 

The Benzo Fast Copper (I.G. Farbenindustrie) and the Cuprophenyl (Geigy) dyes are converted to insoluble copper complexes on the fiber by treating the dyeings with a copper salt. Copper complex formation on the fiber has strongly lost technical significance due to the copper content in dyehouse effluents. The mostly copper-containing Indosol direct dyes recently launched by Sandoz are cross-linked on and with the fiber by aftertreatment with a special reactive agent [35],... 

Amongst the N,S-azole ligands [8,13], benzo-2,l,3-thiadiazol deserves a special mention. The controversial question about the possibility of one particular kind of coordination within the complexes formed from benzo-2,l,3-thiadiazol, one in which only one atom of the heterocycle, either N or S, was able to participate [8,13], was solved by x-ray structure studies in favor of the N-coordination 489 [882], However, the examples of the kinds of coordination presented by the sulfur atom in the thiophene cycle (Sec. 2.2.4.5) do not exclude the possibility of M — S binding, particularly when using softer (i.e., Pt, Pd) Pearson acids. 

The synthesis of 4-azaazulenones is treated in a special section because of the similarities of the synthehtic methods as well as the properties of the topologically correlated 7t-systems. Benzo derivatives with additional substituents that do not fit the relations were covered in preceeding sections. 

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