O-Bromonitrobenzene

A related Heck reaction of substituted o-bromoacetanilides with styrenes followed by selenium-induced cyclization of the resulting o-styiylacetanilides gives 2-arylindoles [378], Substituted o-bromonitrobenzenes react with ethyl vinyl ether under the influence of Pd(OAc)2 to give the corresponding o-ethoxyethenylnitrobenzenes. Zinc reduction then yields indoles [379]. The one-step Pd-catalyzed conversion of o-bromoanilines to indoles 302 with enamines (or with A/-vinyl-2-pyrrolidone) has been reported [380]. 

Fuostifoline (47), a furo[3,2-a]carbazole, was isolated from Murraya euchrestifolia. Timdri s total synthesis of 47 commenced with alkylation of bromocresol 43 with bromoacetaldehyde diethyl acetal and P4Oio-promoted cyclization to furnish 5-bromo-7-methylbenzofuran (44) [47]. The Suzuki coupling of boronic acid 45, derived from 44, with o-bromonitrobenzene yielded biaryl 46. Nitrene generation, achieved via deoxygenation of nitro compound 46 using triethyl phosphite, was followed by cyclization to fuostifoline (47). 

Bromine is an ortho, para-directing group. If it is introduced first, nitration of the resulting bromobenzene yields a mixture of o-bromonitrobenzene and p-bromonitrobenzene. 

Thienoisoquinolines can be prepared in high yields by the palladium cross-coupling reaction of o-formylarylboronic acids with aryl halides. By this method, thieno[3,2-c]- (102), thieno[3,4-c]-(103), and thieno[2,3-c]isoquinolines (104) have been prepared in yields of 90%, 52%, and 75%, respectively (Scheme 48) <86CS3il, 89JHC865). This method was unsuccessful for the preparation of thieno[3,2-c]quinoline A-oxide and thieno[3,2-c]isoquinoline A-oxide. The former compounds were readily prepared via a modification of the reaction using a palladium-catalyzed coupling reaction between 2-tributylstannyl-3-thiophenecarboxaldehyde and o-bromonitrobenzene, while the isoquinoline A-oxide was prepared by mcpba oxidation of the parent compound <90JHC1127>. 

Studies have also been conducted on electrode processes where homogeneous chemical reactions are coupled to heterogeneous electron transfer(s). In this example, the reductive dehalogenations of 3- and 4-bromobenzophenone and of o-bromonitrobenzene (denoted as ArBr) dissolved in N,N-dimethylformamide solution were studied (Compton et al., 1996b). The one-electron reductions of these compounds result in the formation of the corresponding chemically reactive radical anions as shown in (96), where HS denotes the solvent/supporting electrolyte system. 

In the latter preparation, the dichloroarsine is obtained from 2-nibro-diphenylamme-Q -arsinic add. This is prepared by the condensation of o-aminophenylarsinic acid and o-bromonitrobenzene in amyl alcohol in the presence of copper powder and potassium carbonate. It crystallises in golden-yellow ne les, melting with decompositioir at 288° to 240° C. "When reduced in alcoholic concentrated hydrochloric acid solution by sulphur dioxide in the presence of iodine, it yields 2-nitro-diphenylamine-6 -dichloroarsine, which crystallises from benzene-light petroleum in deep red crystals, M.pt. 110° C. 

Cohen, T., Cristea, I. Kinetics and mechanism of the copper(l)-induced homogeneous Ullmann coupling of o-bromonitrobenzene. J. Am. Chem. Soc. 1976, 98, 748-753. 

In addition to reactions initiated with copper metal, reactions have been conducted with copper salts, such as copper oxides, alloys and coordination complexes. Reactions with many bases in several polar solvents have also been explored. Diphenylamine and o-bromonitrobenzene couple with stoichiometric amounts of copper(I) oxide and copper(I) bromide in DMA (equation 59)234. The synthesis of triaryl amines from aryl iodides and arylamines in one-pot proceeds in the presence of Cul and potassium tart-butoxide at 135 °C235. The highest yields were obtained with aryl iodides and electron-rich arylamines. 

Reaction of the chloropyrazine 2 with furan afforded the 2-arylfuran. 2-Arylation of benzo[ >]furan (4) occurs with o-bromonitrobenzene (3) [3b]. Regioselective 2-arylation of ethyl 3-furancarboxylate with 3 occurred to give 5 in 80 % yield when Pd(PPh3)4 and AcOK were used in toluene. 5-Arylation was the main path when ligandless Pd/C was used in the polar solvent NMP. The furo[3,2-c]quinolinone 6 was obtained after hydrogenation of the nitro group [4]. 

The hydrodehalogenation of o-bromonitrobenzene with Pd and Hj to give nitrobenzene is usually unsatisfactory, but under transfer hydrogenation conditions with triethy-lammonium formate a 91% yield of nitrobenzene was obtained. ... 

A mixture of o-bromonitrobenzene and baker s yeast in distilled water incubated at 31-35° for 74 h - o-bromoaniline. Y 62% (72% conversion). Reaction is facilitated by electron-withdrawing groups (CN, NO2, CF3, C02Et) in the ring. F.e.s. M. Take-shita et al., Chem. Pharm. Bull. 27, 615-7 (1989). 

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