Substituents bromo

The patended method of preparation of the blue dye (120) [19187-01 -0] (81) involves treating the analogous dibromo substituted azo dye with cuprous cyanide in dimethylformamide or A-methylpyrrohdinone at 50°C to effect replacement of the two bromo substituents by cyano groups. 

Same stmcture as isoviolanthrone violet, but the chlorine substitution pattern is Same ring stmcture as isoviolanthrone violet, but one bromo substituent rather... 

The presence of an a-bromo substituent may cause anomalies. With NaBH4, 2a-bromo-5a-cholestan-3-one gives a mixture of epimers, in which the 3p-o predominates. 4 -Bromo-17)5-hydroxy-5)5-androstan-3-one acetate gives 25% of the 315,4 -bromohydrin and 34% of the 3a,4)5-compound. Reduction of 7a-bromo-3)5,5a-diacetoxycholestan-6-one gives exclusively 7a-bromocholestane-3)5,5a,6a-triol 3,5-diacetate,whereas reduc-... 

Addition of dimethylsulfoxonium methylide to the a-face of A -20-ketones, A -5a-H-ketones and A " -3-ketones results in the formation of the corresponding 16a,17a-methylene (1), la,2a-methylene-5a-H (2) and la,2a-methylene-A" steroids (3), respectively. Smooth reaction is also observed in the presence of 2-chloro and 2-bromo substituents in the A -5a-H-3-ketone series.Yields of 90% are obtained within a reaction period of 5 hr at room temperature. A A -3-keto system in (1) is not attacked under these conditions. 

The transformation of the hydrophobic periphery composed of bromo substituents into a hydrophilic wrapping of carboxylic acid functions was achieved by reacting 31 with (i) n-butyllithium and (ii) carbon dioxide. The polymer-analogous transformation provides water soluble, amphiphilic derivatives of 31 which constitute useful covalently bonded unimolecular models for micellar structures. 

Oxabicyclo[4.1.0]hept-3-enes with a bromo substituent in position 2 can be converted to oxepins 11 by reaction with an appropriate base such as potassium ter+butoxide or triethylamine (see the experimental procedures for the preparation of the parent system in Houben-Weyl, Vol. 6/ld, pi78 and Vol. 6/4, p462).12,156,157 Usually the reaction products are mixtures of oxepin 11 and benzene oxide 12. In the case of ZerZ-butyl 7-oxabicyclo[4,1.0]hept-3-ene-2-carboxylate, the equilibrium lies completely on the benzene oxide side 12a.158... 

The bromo substituent in 10-bromodibenz[/>,/]oxepin can be replaced by nucleophiles. With copper(I) cyanide in the presence of pyridine, dibenz[fr,/]oxepin-10-carbonitrile (3) is obtained.161 The substitution of bromine by various TV-substituted piperazines to give dibenz[/>,/]oxepins 4 has been accomplished using potassium cm-butoxide.197 This latter reaction probably proceeds via an intermediate with a C-C triple bond.160... 

The bromo substituent in l-bromo-19-meLhyl-l,l9-dideoxybiladienes- c is not essential for porphyrin formation. When 1-methylbiladiene-ac dihydrobromide or the 1,19-dimethyl-biladienc-ac are heated in refluxing methanol or dimethylformamide in the presence of cop-per(II) salts, the porphyrin copper complexes 13 are formed by oxidative cyclization. The free porphyrins can then be obtained by removal of the copper with acid. A wide range of porphyrins 13 can be prepared by this method. However, a restriction is the accessibility of the starting material with special substitution patterns. 

A transition state assembly as depicted in Scheme 1.23 was proposed in order to interpret the observed selectivity. Electronic effects are thought to be operative, as the methyl and bromo substituents in transition state 83 are sterically similar. 

Gore et al.426 have used chloroform as a solvent for acetylation catalysed by aluminium chloride and at 45-55 °C find that a 2-methoxy substituent in naphthalene increases the reactivity of the 1 position 1.72 times, of the 6 position 3.8 times, and of the 8 position, 0.9 times the former and latter of these results indicate a considerable steric effect. Likewise, a 2-bromo substituent caused the reactivity of the 6 and 8 positions to be 0.63 and 0.58 times that of the corresponding positions in the unsubstituted compound. At 20-25 °C the relative reactivities of some polycyclics were as follows427 1-naphthyl, 1.0 3-phenanthryl 0.64 9-phenanthryl, 0.02 1-phenanthryl, 0.29 2-naphthyl, 0.28 2-phenanthryl, 0.12 4-phenanthryl, 0.0085. Some of these results seem to be due to steric hindrance, and the large difference in reactivity of naphthalene and biphenyl seems erroneous. 

The transformation of the terminal bromo substituents to carboxylic acid functions with (i) n-butyl lithium (ii) carbon dioxide, provides water soluble derivatives of 47 which are interesting as models for unimolecular micelles. 

DMA. Introduetion of a 5-methyl or 5-bromo group, to produce 5-methyl-2,4-DMA and 5-bromo-2,4-DMA, results in active agents, but they are not signifieantly more potent than 2,4-DMA itself. It seems that the methyl and bromo substituents are tolerated at the 5-position, but they do not produce the increase in activity seen in the 2,5-DMA series. 

Recently, Traynelis and his coworkers 221 have reported the thermal decomposition of some substituted benzo[6]thiepins (Table 2). A slight increase in the stability of the thiepin ring by phenyl, benzyl, methyl, chloro, and bromo substituent was... 

The influence of the number and orientation of bromo substituents on heat fastness in two systematic series of multibrominated derivatives of 1,5-diaminoanthrarufin (3.185) and... 

The Delft synthesis makes use of an acid-catalyzed ring closure - in fact an intramolecular aromatic alkylation - of a l-(3,5-dihydroxy-4-methoxybenzyl) isoquinoline derivative that is prepared starting from (natural) gallic acid. One of the hydroxyl groups is removed via a Pd/ C hydrogenation of the benzyl ether. Other catalytic steps play an important role some steps were improved recently [27]. The crucial step in the Rice synthesis makes use of a l-(2-bromo-5-hydroxy-4-methoxybenzyl)isoquinoline derivative that is also cyclized in an acid-catalyzed ring closure to the morphinan skeleton, followed by catalytic removal of the bromo substituent (Scheme 5.8). 

We thus obtain defined, monodisperse, defect-free functionalized dendrim-ers, which are easily purified due to the high mass differences between the cyclopentadienone and the final dendrimer. However, for each new functionality, an appropriate cyclopentadienone building unit has to be synthesized. This can be achieved via a double Knoevenagel reaction of an already functionalized benzil 35 and diphenylacetone 24. For example, 4,4 -dibromobenzil (35a) as well as 4,4 -dimethoxybenzil (35 b) are commercially available and give the cyclopentadienone building unit with two bromo- or methoxy substituents in high yields [30, 34]. Furthermore the bromo substituent of the dibromocyclopenta-dienone can be quantitatively converted into a cyano (37) or amino (38) function (Scheme 13) [52]. 

Treatment of the halides 16 with an alcohol promoted by silver salts does yield mainly the p-glycosides 17 (28. 29[,). Obviously the bromo substituent directs the incoming nucleophile by steric reasons or possibly via a 1,2-bromonium<->bromo-oxocarbenium intermediate. Following a reduction step, the syntheses of p-glycosides 18... 

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