Bromotoluenes methylation

Thus, ( + )-isocomene was prepared in five steps from 2-bromotoluene, methyl vinyl ketene and (Z)-2-bromobut-2-ene. According to the synthetic strategy the key step is the intramolecular meta photocycloaddition of (Z)-3-methyl-6-(2-tolyl)hept-2-ene. By irradiation in cyclohexane at room temperature for four hours, a 1 1 mixture of isomeric photoadducts was obtained in 72 % yield, the constituents of which were easily interconverted photochemically. Thermolysis of the vinylcyclopropanes at 235-240 C gave dehydroisocomene in 57% yield, which was finally hydrogenated over 5 % palladium on carbon to give the expected sesquiterpene in 98% yield. ... 

Yields of 54% of 2-methoxy-4 -methyl diphenyl ether from -bromotoluene and guaiacol, and 60% of 2-mcthoxy-5-methyl-diphenyl ether from 3-bromo-4-methoxytoluene and phenol, have been obtained by the same method in the laboratory of the submitters,... 

The Md NMR spectrum of /)-bromotoluene, shown in Figure 15.15, displays many of the features just discussed. The aromatic protons appear as two doublets at 7.02 and 7.45 8, and the benzylic methyl protons absorb as a sharp singlet at 2.29 8. Integration of the spectrum shows the expected 2 2 3 ratio of peak areas. 

Next ask yourself, "What is an immediate precursor of p-bromotoluene " Perhaps toluene is an immediate precursor because the methyl group would direct bromination to the ortho and para positions. Alternatively, bromobenzene might be an immediate precursor because we could carry out a Friedel-Cralts methylation and obtain a mixture of ortho and para products. Both answers are satisfactory, although both would also lead unavoidably to a product mixture that would have to be separated. 

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... 

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). 

The relay compound 1025 required for the synthesis of all of these 7-oxygenated carbazole alkaloids was obtained starting from commercially available 4-bromo-toluene (1023) and m-anisidine (840) in two steps and 72% overall yield. Buchwald-Hartwig amination of 4-bromotoluene (1023) with m-anisidine (840) furnished quantitatively the corresponding diarylamine 1024. Oxidative cyclization of 1024 using catalytic amounts of palladium(ll) acetate afforded 3-methyl-7-methoxycarbazole (1025). Oxidation of 1025 with DDQ led to clauszoline-K (98), which, on cleavage of the methyl ether using boron tribromide, afforded 3-formyl-7-hydroxycarbazole (99) (546) (Scheme 5.149). 

The same method may be used for the preparation of tri- -tolyl-stibine. Starting with 282 g. of -bromotoluene (Org. Syn. 6, 21) and proceeding in the same manner as described there was secured 150-157 g. (77 -80 per cent of the theoretical amount) of crude tri-/>-toIyl-stibine. This product purified by recrystallization from methyl alcohol or ether melts at 125-126°. The reaction is somewhat more vigorous in this case and sometimes cooling is necessary at first. 

The following couples were tested p-chlorobenzonitrile/p-chloro-acetophenone, p-chloroacetophenone/p-chlorodiphenyl, p-chlorodiphenyl /chlorobenzene, p-chlorodiphenyl/p-chlorofluorobenzene, chlorobenzene /p-chlorotoluene, chlorobenzene/p-chloroanisole, p-chloroacetophenone/ methyl ester of m-chlorobenzoic acid, chlorobenzene/m-chlorotoluene, p-chlorodiphenylether/p-chlorotoluene, m-chlorodiphenylether/chloroben-zene, m-chlorodiphenylether/p-chlorotoluene, chlorobenzene/methyl ester of m-chlorobenzoic acid, chlorobenzene/p-bromoanisole, p-bromoaceto-phenone / p-chlorobenzonitrile, p-bromobenzonitrile / p-chloroacetophe-none, bromobenzene/p-chlorodiphenyl, m-bromotoluene/chlorobenzene, and p-chlorodiphenyl/p-bromotoluene. 

Ethyl-l-Methyl-benzene, CH3C6H, C2HS mw 120.20, oil, sp gr 0.8588 at 20°/4fbp I62°nc 1.4929 at 24.4°. Prepd from 4-bromotoluene, ethyl bromide and sodium in eth... 

SYNS (BROMOMETHYL)BENZENE p-(BROMO-METHYL)NITROBENZENE BROMOPHENYL-METHANE (O-BROMOTOLUENE P [Pg.151]

The methyl hydrogens of toluene are relatively inert to the attack of these charged particles. In contrast, the polarizable 7t-electron system of the aromatic nucleus can be easily perturbed by the approach of the bromine cation. In a simplified form, their interaction can be described in the sequence of the following steps. The attacking cation pulls an electron pair of the aromatic system towards itself to form a C-Br bond. A concerted shift of the next electron pair leads to the development of a positive charge on the methylbearing para-carbon atom. Loss of a proton from this c-complex 13 leads to the formation of bromotoluene with restoration of the aromaticity in the system. Besides the para isomer of bromotoluene 8, the corresponding ortho isomer is also formed, but in lesser amounts. 

Stevens and Bisacchi have carefully examined the trailing of benzynes, generated fiom a number of aryl bromides and sodium amide in THF, with 1,1-dimethylethylene and report procedures which afford 6 6% yields of 1,1-dimethoxycyclobutenes, e.g. (131). These compounds are hydrolyzed quantitatively to the corresponding benzocyclobutenones (132). Excellent regioselectivity was obtained with unsym-metrical benzynes derived from methoxy substituted bromobenzenes due to the polarized nature of the benzyne intermediate. Steric effects also influence regioselectivity o-bromotoluene afforded a 3 1 mixture of 3-methyl- and 6-methyl-benzocyclobutene. 

Di-o-tolylmethylarsine, (C7H7)jAs.CH3, is isolated by the interaction of the Grignard reagent derived from o-bromotoluene with methyl-di-iodo arsine. It melts at 42° C., giving a very pale, yellow oil, B.pt. 178° to 182° C. at 12 mm. 

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