Arylation nitrotoluene

Sulfones with an additional electron-withdrawing a-substituent can be smoothly arylated in the presence of PPh3 as ligand (50).199 Similar methods were developed for the a-arylation of nitrotoluene and alkylazines (51).200... 

Complementary experiments, conducted in the same conditions but in the absence of nitric acid, show that MDPM are not formed neither from toluene nor from nitrotoluenes. In the case of an acid catalysis by protons only, condensation of toluene should lead primarly to the isomers of dimethylbiphenyls by an "arylation - dehydrogenation sequence. However, these products are not observed. 

Bromine adds to the alkene but substitutes on the aryl ether, evolving gaseous HBr. 17.10. Strong acid is used for nitration, and the amino group of aniline is protonated to a deactivating — NH3+ group. 17.12. (a) 2,4- and 2,6-dinitrotoluene (b) 3-chloro-4-nitrotoluene and 5-chloro-2-nitrotoluene (c) 3- and 5-nitro-2-bromobenzoic acid ... 

Bis(4-methyl-2-nitrophenyl)trisulfane is formed in 84% yield on reaction of 4-chloro-3-nitrotoluene with molten sodium polysulfide. Other aryl halogenides have also been converted to trisulfanes by ionic polysulfides. ... 

The preparation of aryl halides from diazonium salts is more important than direct halogenation for several reasons. First of all, fluorides and iodides, which can seldom be prepared by direct halogenation, can be obtained from the diazonium salts. Second, where direct halogenation yields a mixture of ortho and para isomers, the ortho isomer, at least, is difficult to obtain pure. On the other hand, the ortho and para isomers of the corresponding nitro compounds, from which the diazonium salts ultimately come, can often be separated by fractional distillation (Sec. 11.7). For example, the o- and />bromotoluenes boil only three degrees apart 182° and 185°. The corresponding o- and -nitrotoluenes, however, boil sixteen degrees apart 222° and 238°. 

Arylations. A rather unusual reaction for the synthesis of triarylmethanes is that which involves benzylic arylation of 4-nitrotoluene and homologs catalyzed by Pd(OAc)2-PhjP in the presence of CS2CO3. One or two aryl groups can be introduced by this method. Arylation of amines by ArX employs the Pd(OAc)2-f-BuONa and a phosphine as catalyst. Pentaarylcyclopentadienes are readily formed in a reaction of metallocenes (nickelocene, titanocene dichloride, zirconocene dichloride) with ArBr in... 

Friedel-Crafts based cyclization reaction was also developed to realize the key intermediate for the synthesis of bergapten <05H(65)1985>. A structurally diverse series of 2-aryl-5-substitut -2,3-dihydrobenzo[4>]furans was made via a rapid and efficient base-mediated one-pot reaetion from o-nitrotoluene and aromatic aldehydes <05JOC3727>. 

Condensation ofNitro Compounds. The stflbene dyes derived from condensation of 4-nitrotoluene-2-sulfonic acid [121-03-9] (para acid) in aqueous caustic solution either alone or with aryl amines, are mixtures of dyes containing azo and azoxy groups with indefinite structures. The primary products are 4,4,-dinitro-2>2,-stilbenedisulfonic acid [128 42-7] and 4,4,dinitrodibenzyl-2>2,-disulfonic acid [6404-60-0] which condense further to form the dye. The properties of the stilbene dyes vary with the amounts and concentrations of the reactants and with the time and temperature of heating. The hue... 

Indoles and Carbazoles. - Formation. 2-Arylindoles (132) are formed by intramolecular Wittig reaction of the phosphonium salts (131). The hydroxamic acids PhN(OH)COCH2COR (R = alkyl or aryl) cyclize in boiling toluene to mixtures of indoles (133) and 3-isoxazolones (134). Irradiation of a solution of o-iodoaniline and the potassium enolate of acetone affords 2-methylindole. The enamino-ketone (135) cyclizes photochemically to 1,2-dimethylindole (136) with elimination of acetaldehyde/ The styrene derivative (137), obtained by the action of Meerwein s acetal, Me2NCH(OMe)2, on o-nitrotoluene, yields 1-hydroxyindole on treatment with zinc/ Azidobenzocyclobutanes (138 R = Me, Ph, or CH2Ph) are converted into indoles (133) by the action of concentrated sulphuric acid/ ... 

Nitroalkanes are monoarylated effectively by using a biphenylphosphine and CS2CO3 as ligand and base, respectively (Eq. 27) [20, 72]. The intramolecular version has been reported [57]. Interestingly,4-nitrotoluene undergoes formal vinylogous arylation, while 3-nitrotoluene is inactive [73]. Thus, 3,4-dimethyl-nitrobenzene is selectively arylated at the 4-methyl group (Eq. 28). 

Furthermore, arylation of the methyl group of p-nitrotoluene (95) with bro-mobenzene occurs at 140°C using CS2CO3. As a ligand PPhs is effective [50], Both the monophenylated product 96 and the diarylated one 97 were obtained selectively depending on the reaction conditions. 

As expected, less activated 3-nitrotoluene was not arylated, and the monoary-lated product 100 was obtained selectively from 3,4-dimethylnitrobenzene (99) and sterically hindered 2-bromo-l,4-dimethylbenzene (98). On the other hand, diary-lation of 4-methylpyrimidine (101) with 2-bromo-l,4-dimethylbenzene (98) gave 102 smoothly. No arylation of 4-methylbenzonitrile occurs. 

This new indole ring synthesis should find utility for the preparation of 2-aryUndoles with electron-withdrawing substituents in the indole ring. Furthermore, as we see in equations 1-3, the bromine atom is impervious to attack by the Grignard reagent. The starting ortfto-nitrostilbenes were prepared in the standard fashion from the appropriate ortho-nitrotoluene and aryl aldehyde with piperidine as base. 

Figure 10.3. Aryl derivatives (clockwise from the top) 4-chloro-l-methylbenzene (4-chlorotoluene), methylbenzene (toluene), 4-cyano-l-methylbenzene (4-cyanotoluene), 4-fluoro-l-methylbenzene (4-fluorotoluene), 4-nitro-l-methylbenzene (4-nitrotoluene) prepared by copper(I) salt-catalyzed decomposition of the diazonium salt generated on treatment of 4-amino-l-methylbenzene, (4-aminotoluene) with sodinm nitrite (NaN02), and protic acid.

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