Benzene moiety

Attempts to brominate benzothiazoles with bromine in acetic acid at room temperature have given only perbromides, but when these were heated in ethanolic solution, products in which bromine had substituted in the benzene moiety were detected. At 100°C bromine in acetic acid gave rise to the 4,6-dibromo derivative in accord with calculated -densities (70BSF2705). Vapor-phase bromination gave the 2-bromo product (84MI27). 

Whereas benzopyrylium salts are resistant to electrophilic substitution, even in the benzene moiety, the benzopyrones [coumarins (81), isocoumar-ins (82), and chromones (83)] are readily halogenated in either ring, with... 

Unsubstituted benzobicyclo[2.2.2]octatriene 76a bearing two methoxycarbonyl groups at the and C3 positions exhibited strong anti preference (with respect to the benzene moiety) with two oxidative electrophilic reagents, m-chloroperbenzoic acid (mCPBA) and osmium tetroxide. 

Another limitation of the traditional Cu-mediated cyclooligomerization reaction is generation of differentially substituted PDMs. In the above case, the substitution pattern in the starting o-diethynylbenzene must be maintained on each and every benzene moiety in the oligomeric mixture of PDMs that is produced. Thus, it is impossible to prepare less symmetric systems like 100 via this route. With the intramolecular synthetic approach, however, it should be possi-... 

Fig. 8 Structure-photophysical properties relationship of fluorescein derivatives. Measured in 0.1 N NaOH(aq). bOxidation potential of corresponding benzene moiety, obtained in acetonitrile containing 0.1 M TBAP. °HOMO energy level of the corresponding benzene moiety, calculated with B3LYP/6-31G(d)//B3LYP/6-31G(d) by Gaussian 98 W...

As can be seen, in both the 5,6- and the 7,8-dihydroxy-2(lH)quinolinone pathways, after initial hydroxylation adjacent to the N-heteroatom, the benzene moiety of the quinoline ring is transformed to a dihydroxy derivative 5,6- or 7,8-, respectively, which subsequently undergoes ring cleavage. However, neither of them involves C—N bond cleavage and consequently do not lead to denitrogenated products. 

Reaction of 6-halopurines with Michael acceptors under Heck conditions gives N- -substituted hypoxanthine derivatives <00CCC797>. Reactions of a series of 1-aminobenzimidazoles and l-amino-3-methylbenzimidazolium chlorides with 2,4-pentanediones afford pyridazino[l,6-a]benzimidazoles and 2-pyrazolylanilines, the product ratio depending on conditions and on the electronic character of the substituents at the benzene moiety <00BMC37>. Cyclization reactions of adenine derivative 75 with different amines or hydrazine afford tricyclic polyaza compounds 76 <00CCC1109>. 

These compounds contain a furan ring fused to a benzene moiety in the 2,3-position. This synthesis was also described by Flynn et al. [73] and is shown in Scheme 25 involved the coupling of 2-iodo-5-methoxyphenol 104, 4-methoxyphenylethyne 105 to form the intermediate o-alkynylphenolate 106. Aryl iodide 107 was added to the phenolate in DMSO with heat. Oxidative addition, palladium(II)-induced cyclization and reductive elimination resulted in the product 108 with an 88% yield. 

Kline, T., Benington, F., Morin, R. D., and Beaton, J. M. (1982) Structure-activity relationships in potentially hallucinogenic N,N-dialkyltryptamines substituted in the benzene moiety. J. Med. Chem., 25 908-913. 

A similar strategy has been applied by Mazik and coworkers. The receptor is usually titrated with increasing amounts of the sugar, to evidence binding, to extract the values of the binding constants and to get the stoichiometry of the complexes formed. Reverse titrations and extraction experiments can also be performed. The structures of the receptors described are based on different scaffolds the above mentioned hexasubstituted tripodal benzene moiety and 3,3, 5,5 -tetrasubstituted... 

The following compounds which have a benzene moiety of [2.2]para-cyclophane replaced by a heteroring (e.g. furan) may be counted among the analogs of [2.2]paracyclophane, as their stereochemistry has many features in common with that of the carbophanes 64> 34—36. 

Another pyridazinone-derived inotropic agent with cAMP phosphodiesterase inhibitory activity is pimobendan [UD-CG-115-BS CAS 74150-27-9, (21)], which has been developed in Germany. In contrast to the imidazolyl-phenylpyridazinone CI-930 (16) discussed above, in pimobendan the imidazole nucleus (substituted at C-2 by a 4-methoxyphenyl group) is fused to the benzene moiety attached to C-6 of the 4,5-dihydro-5-methyl-3(2//)-pyri-dazinone system. 

In addition to the dihydropyridazinones discussed above, the patent literature covers a wide variety of 6-phenyl-substituted derivatives in which the benzene moiety is either further substituted or annulated to a heterocyclic... 

The oxidative degradations of binuclear azaarenes (quinoline, isoquinoline, and benzodrazines) by hydroxyl and sulfate radicals and halogen radicals have been studied under both photochemical and dark-reaction conditions. A shift from oxidation of the benzene moiety to the pyridine moiety was observed in the quinoline and isoquinoline systems upon changing the reaction from the dark to photochemical conditions. The results were interpreted using frontier-orbital calculations. The reaction of OH with the dye 3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-(l,8)(2//,5//)-acridinedione has been studied, and the transient absorption bands assigned in neutral solution.The redox potential (and also the pA a of the transient species) was determined. Hydroxyl radicals have been found to react with thioanisole via both electron transfer to give radical cations (73%) and OH-adduct formation (23%). The bimolec-ular rate constant was determined (3.5 x lO lmoU s ). " ... 

Attempts to lithiate the benzene moiety of 1,4-dimethoxyphthalazine and of l-methoxy-4-phenylphthalazine were unsuccessful. However, treatment of 6-chloro-l,4-dimethoxyphthalazine with Bu"Li results in the regioselective lithiation at C-7 <1999T5389>. 

This provides a simple route to difficult-to-obtain compounds of the 4,5-dihydrobenzo[g]indole series, which are rather promising in the search for new bioactive substances and dyes. 4,5-Dihydrobenzo[g]indole (see Table XIX) was isolated by column chromatography (A1203, Et20/hexane 1 2) as colorless crystals that turn blue in air. The H-NMR spectrum of pyrrole 36 (CDCI3, ppm) shows 7.1 m (four benzene protons) 6.8 t and 6.0 t (two pyrrole protons) and 2.8 m (four protons in positions 4 and 5). The IR spectrum shows the characteristic bands of the pyrrole and benzene moieties (cm-1) 695, 730, 765, 1510, 1560, 1580, 1610, 3040, 3050, 3100, 3390, and 3430. 

In the cases of 170, 171,75-79 and 45, the resonance energy of the benzene moiety ( 39 kcal) trips the stability order irretrievably on the side of oxepin in the first two cases and in favor of arene oxide in the case of 45. Tautomerism, which ordinarily is manifested with systems having small energy differences, is therefore ruled out. However, in the case of the 9,10-oxide this limitation does not exist, but even so, the compound exists only in the oxepin form (70),8 possibly because of a very high strain on the oxirane ring in the epoxy form. 

The results are to some extent inconclusive and suggest that a two-photon state may have to be included. Also reported here are some further major improvements in molecular second order nonlinearities of particular importance to poled-polymer electrooptic applications (EO). Thus, it is found that appropriate replacement of benzene moieties with that of thiazole in certain azo dyes results in a factor of three increase in i-p, the molecular dipole ( io) projected molecular second order nonlinear optical susceptibility, p. 

Hiickel calculations of Siegel cyclohexatriene with inclusion of /3-parameters between the bridge jr orbital and the jr orbitals of the benzene moiety change the bond orders and predict the direction of bond alternation observed in the molecule. Heil bronner, E. Personal communication to S.S. 

The protonated dendrimer exhibits a far more intense excimer band than corresponding Frechet dendrons without a cyclam core. One possible reason for this behaviour is that excimer formation is facilitated by folding of the - flexible - benzyl ether framework. Whereas a change in emission intensity is observed in the course of protonation of the cyclam dendrimer, a reference substance containing no cyclam and benzene moieties (Fig. 5.17) shows a linear increase... 

Diacyloxyiodo)benzenes like 3 and 4 have been especially popular for the oxidation of phenol derivatives. Recently some electronically modified reagents of this type have been synthesized, where the benzene moiety has been replaced by a heteroaromatic system. For compounds 15-17 see Scheme 3. The reagents 15 and 16 have been used for oxidations of hydroquinones and sulfides as well... 

For example, Hayashi et al. (73) recently reported an enhancement of the peroxidase activity of Mb by modification of two heme-propionate side chains. They prepared an artificial hemin having two benzene moieties linked at each terminal carboxylate of the heme-propionates in protoheme IX, as shown in Fig. 18. The modified hemin was then inserted into the horse heart apoMb to yield a reconstituted Mb. The characterization of the reconstituted Mb was carried out by ultraviolet-visible (UV-vis), NMR, and electronspray ionization-mass spectrometry (ESI-MS). Particularly, the UV-vis spectrum of the reconstituted Mb is comparable with that observed for the native Mb, suggesting that the artificial hemin is located in the normal position of the heme pocket. 

Pie, N. Turck, A. Chapoulaud, V. Queguiner, G. First functionalization by metalation of the benzene moiety of quinazolines. Diazines XIX. Tetrahedron 1997, 53, 2871-2890. 

The structure—activity relationship of the series of compounds shows that the most active compounds are 6-phenylpurine nucleoside 12a and its congeners bearing a functionality in position 4 of the benzene ring (compounds 12b, 12g, 12i, and 12j). Introduction of a substituent into position 3 of the benzene moiety causes a substantial decrease of activity (compounds 12d and 12h), while the presence of a substituent in position 2 leads to inactive compounds (12c and 12e). Also the presence of an amino function in position 2 of the purine ring causes loss of activity. The acetyl derivatives 8 of... 

---