2-Bromotoluene, reaction with

For instance, bromination of toluene in carbon tetrachloride did not proceed at reflux, even though pentamethylbenzene was brominated at 30°C to give bromopentamethylbenzene quantitatively. Toluene and copper(II) bromide reacted at reflux for 72 h. to give benzyl bromide as the main product. In a similar reaction with alumina-supported copper(II) bromide, bromotoluene (o/p = l) was obtained in good yield and no side-chain-brominated compounds were detected. 

It was of interest to see if the use of tm-butyl hypobromite would provide similar opportunities for regioselectivity to those found in the case of chlorination reactions with te/t-butyl hypochlorite. The initial indications were favourable use of H zeolite X as catalyst in dichloromethane solution gave an almost quantitative yield of bromotoluenes with a para ortho ratio of 81 19 (Fig. 5) (ref. 10). 

A nontraditional type of photochromic dihetarylethenes bearing a six-membered aryl moiety was described (08T9464). Compounds 34 were prepared from 2-methyl-5-phenyl-3-thienylperfluorocyclopentene by a one-step coupling reaction with 2-bromoanisole, 2-bromotoluene, 2-bro-mobenzonitrile, and 2-bromobenzotrifluoride, respectively (Scheme 12). 

SAMPLE SOLUTION (a) Reaction with ethylene oxide results in the addition of a —CH2CH2OH unit to the Grignard reagent. The Grignard reagent derived from o-bromotoluene (or o-chlorotoluene or o-iodotoluene) is appropriate here. 

Figure 2.2 Pressure profiles recorded from microwave heating at 180°C of (A) formamide and KOf-Bu (B) a preparative aminocarbonylation reaction with 4-bromotoluene and formamide and (C) pure formamide (Smith Synthesizer).

Hartwig reported that ferrocene-based diphosphine 13 catalyzes the arylation of aniline at room temperature, Eq. (91) [72]. Additionally, the (f-BuljP/Pd-based system effects the room-temperatuxe condensation of anilines and aryl bromides. However, the (f-BuljP/Pd-catalyst is considerably more active [50]. While the reaction with 4-bromotoluene and anihne proceeded in 20 h using 5 mol% 15/Pd(dba)2, the reaction between bromoben-zene and aniline was complete in 1 h using only 1 mol% of the (f-BuljP-derived catalyst. 

Palladium complexes of Q-phos (14, Figure 5) are also active catalysts for the coupling of aryl bromides with diarylamines67. Reactions of aryl bromides occurred at room temperature, even for the somewhat sterically hindered 2-bromotoluene. Reactions of aryl chlorides catalyzed by the same complex required heating at 100 °C, but formed the triarylamine in nearly quantitative yield. 

Catalysts generated from A-heterocyclic carbenes 23-25 (Figure 7) have been shown to efficiently catalyze the coupling of aryl and heteroaryl halides with indoles. Reactions conducted with the terf-butoxide base, which is typically used for the C—N coupling, did not occur, but reactions with NaOH as base occurred to high conversion85. Although 4-bromotoluene and bromobenzene reacted with numerous substituted indoles under these conditions, electron-rich and orf/zo-substituted aryl bromides reacted slowly and in low or moderate yields. 

Not every reaction that might pass through arynes always does it. All ortho-, meta-, and para-isomers of fluoro-, chloro-, and bromotoluene produce with TMEDA-activated phenyllithium isomeric mixtures of methylbiphenyls, the proportions of which are halogen-invariant and are in accordance with the intermediacy of 3-methyl- or 4-methyl-1,2-didehydrobenzene, respectively. In contrast, each one of the three iodotoluene gives a sole isomer that has conserved the regiochemistry of its precursor. Similarly, the treatment of or/Ao-fluoroanisole with 2,6-dimethoxyphenyllithium cleanly furnishes the weto-coupled 2, 3,4 -trimethoxybiphenyl-2-yllithium. However,... 

Now let s draw the forward scheme. Conversion of we i-bromotoluene to a Grignard reagent, followed by reaction with carbon dioxide and subsequent acidification, produces weto-methylbenzoic acid. The carboxylic acid is converted to the acid chloride, which then reacts with diethylamine to produce the desired amide, DEBT. 

By the reaction of bromotoluene with ethylene under pressure, p-methylsty-rene and stilbene (45) are obtained[44,45]. A polymer 47 is obtained by the reaction of >-bromostyrene (46) with ethylene. The reaction has been applied to polymer synthesis[46]. One example is the reaction of 1,4-divinylbenzcne (48) with 9,10-dibromoanthracene to give the oligo(arylenevinylene)s 49[47]. 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives The reactivity of a particular position in o bromotoluene for example is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene On the basis of the partial rate factor data given here for Fnedel-Crafts acylation predict the major product of the reaction of o bromotoluene with acetyl chlonde and aluminum chloride... 

The hydrolysis of p-bromotoluene with aqueous sodium hydroxide at 300°C yields i-methylphenol and p-methylphenol in a 5 4 ratio. What is the meta—para ratio for the same reaction carried out on p-chlorotoluene ... 

The substitution reaction of toluene with Br2 can, in principle, lead to the formation of three isomeric bromotoluene products. In practice, however, only o- and jp-bromotoluene are formed in substantial amounts. The meta isomer is not formed. Draw the structures of the three possible carbocation intermediates (Problem 15.48), and explain why ortho and para products predominate over meta. 

In a dry 3-1. three-necked, round-bottomed flask fitted with an efficient reflux condenser, a stirrer, a Y-tube holding a 1-1. and a 250-ml. addition funnel, and protected from moisture by calcium chloride tubes is placed 5.76 g. (0.237 mole) of magnesium turnings barely covered by anhydrous ether, p -Bromotoluene (40 drops) and ethyl bromide (20 drops) are added, and the reaction starts immediately. />-Bromotoluene (35.0 g., 0.205 mole) in 200 ml. of anhydrous ether is added at such a rate that reflux is maintained. To the resultant solution of />-methyl-phenylmagnesium bromide is added, over a 1-hour period, a solution of 25.4 g. (0.200 mole) of dichloroacetone in 200 ml. of anhydrous ether. 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

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