Bromotoluenes synthesis

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]. 

Preparation of Nitriles Investigated in Micro Reactors Organic synthesis 4 [OS 4] Nitrile synthesis from a-bromotoluene... 

Azide Substitutions Investigated in Micro Reactors Organis synthesis 6 [OS 6] Azide substitution of a-bromotoluene... 

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). 

Proceeding with the synthesis in the forward direction, reaction between the Grignard reagent of o-bromotoluene and 5-hexenal produces most of the desired carbon skeleton. 

For the synthesis of orfbo-bromotoluene we use a sulphonic acid. o-Bromotoluene could be synthesised by bromination of toluene or by Friedel-Crafts alkylation of bromobenzene (Fig. T). However, the reaction would also give the para substitution product and this is more likely if the electrophile is hindered from approaching the ortho position by unfavourable steric interactions. Alternatively we can substitute a group at the para position before carrying out the bromination. 

Problem 18.4 What carboxylic acid can be prepared from p-bromotoluene (a) by direct oxidation (b) by free-radical chlorination followed by the nitrile synthesis ... 

To begin with, we might consider some rather simple compounds, the three isomeric bromotoluenes. The best synthesis of each employs diazotization, but not for the same purpose in the three cases. The 0- and p-bromotoluenes are prepared from the corresponding 0- and p-nitrotoluenes ... 

Synthesis of m-bromotoluene is a more complicated matter. The problem here is one of preparing a compound in which two or/Ao,puru-directing groups are situated meta to each other. Bromination of toluene or methylatioh of bromo benzene would not yield the correct isomer. m-Bromotoluene is obtained by the following sequence of reactions ... 

Problem 25.2 Using a different approach in each case, outline all steps in the synthesis of the following from toluene (a) p-bromotoluene (b) p-iodotoluene ... 

Derivation From p-bromotoluene by oxidation. Use Organic synthesis, detection of strontium. 

Blanc reaction. In carrying out the reaction of p-bromotoluene with formaldehyde and a Lewis acid catalyst to obtain the isomeric chloromethyl derivatives for use in a synthesis of methylcholanthrene, Fieser and Seligman18 fused a mixture of anhydrous zinc chloride with 1% of aluminum chloride and let it cool, added p-bromotoluene and paraformaldehyde, and passed a slow stream of hydrogen chloride into the mixture while heating it at 45-50° for 18 hrs. Use of the special catalyst increased the yield about threefold over that obtained with zinc chloride alone. 

It seemed plausible that if the thiolate sulfur were replaced by neutral thioether sulfur then the latter would be more weakly bound to the metal introducing the possibility of hemi-labile coordination. We have therefore investigated the chemistry of some related phosphinothioether complexes of Ru" and Pd". The new ligand 2-MeSCgH4CH2PPh2 (L) was prepared in reasonable yield in a three stage synthesis starting from 2-bromotoluene by bromination to 2-... 

The carboxylic acid formed by free-radical chlorination of p-bromotoluene, followed by nitrile synthesis and hydrolysis is p-bromophenylacetic acid. 

Metal oxides. Beside mesoporous silica materials conventional metal oxides have been applied for the synthesis of solid Pd catalysts for C—C coupling reactions. Alper and coworkers [151] and Singh and coworkers [144] immobilized Pd complexes on a modified silica surface modified by covalent anchoring. The resulting solid catalyst was tested in reactions of several non- and deactivated aryl bromides (bromobenzene, p-bromotoluene, p-bromoanisole) and butyl acrylate or styrene. Only TONs around 100 were achieved after 1 day reaction. 

We can see an example of the usefulness of a deamination reaction in the following synthesis of -bromotoluene. 

The arene-olefin meta-photocycloaddition approach to triquinane natural products is further illustrated this year with a three-step total synthesis of ( )-silphinene (5) starting from 2-bromotoluene (1). Thus, irradiation of the arene-olefin (2) derived from (1) gave a 1 1 mixture of the photoadducts (3) and (4) in 70% yield. Regioselective reductive cleavage of the cyclopropane bond in (3),... 

DEET is the active ingredient in many insect repellents, such as OFF . Starting with meta-bromotoluene and using any other reagents of your choice, devise an efficient synthesis for DEET. 

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