2- Bromo-1 -methylnaphthalenes

P-Naphthaldehyde. This preparation illustrates the use of -bromo-succinimide (Section VI.26) in the conversion of the readily available P-methylnaphthalene into 2-bromomethylnaphthalene and of the latter into p-naphthaldehyde by the Sommelet reaction. 

Bromo-3-methyl-1,4-naphthoquinone 2-Bromo-1,4-dimethoxy-3-methylnaphthalene 88... 

The use of lithionaphthalene and lithio 8-methylnaphthalene as functionally substituted anionic initiators is very disappointing (21, 22). The deactivation of living polyanions onto a-bromonaphthalene or bromo-8-methylnaphthalene is another unsatisfactory approach due to metal halogen interconversion (eqs 9, 10) (23). 

A mixture of 210 g. (0.95 mole) of l-bromo-2-methylnaphthalene (p. 51), 160 g. (0.90 mole) of N-bromosuccinimide (p. 59), 1 g. of benzoyl peroxide, and 250 ml. of carbon tetrachloride is refluxed for 2.5 hours. Carbon tetrachloride (250 ml.) is added, and the warm mixture is filtered. The solid residue is washed several times with fresh carbon tetrachloride. The combined filtrate is concentrated and cooled, and the precipitated product is filtered off. There is obtained 230 g. (85%) of l-bromo-2-bromomethylnaphthalene melting at 103.5-105.5°. 

A small amount of iodine and iron powder is added to a solution of 142 g. (1.0 mole) of 2-methylnaphthalene in 300 ml. of carbon tetrachloride. The mixture is cooled to 0°, and a solution of 160 g. (1.0 mole) of bromine in 300 ml. of carbon tetrachloride is added (8 hours) with stirring and exclusion of light, during which time the temperature is not allowed to rise above 5°. (Hood.) After standing overnight, the solution is washed with 10% sodiiun hydroxide solution and water followed by drying over calcium chloride. Distillation gives 186 g. (84%) of l-bromo-2-methylnaphthalene, b.p. 152-156°/14 mm. 

Molecular diffusion and molecular tumbling are severely restricted in solids. However, in-plane molecular rotation is often observed in the solid state for special aromatic molecules, e.g., the activation energy = 4.69 Itcal/mol and the rate constant )c = 4.7 X 10 s at 25 C for 1-bromo-8-methylnaphthalene... 

The particular value of the method is for converting methyl and polymethyl derivatives of polycyclic aromatic compounds into mono- and poly-carboxylic acids. For instance, 1-methylnaphthalene with a 42% excess of aqueous sodium dichromate solution in an autoclave at 240-250° gives 95% of 1-naphthoic acid in 18 h 2-methylnaphthalene with a 55% excess gives a 93% yield of 2-naphthoic acid the methyl group in fluoro-, bromo-, chloro-, nitro-, and methoxy-toluene as well as in xylenes and heterocycles can usually be oxidized smoothly to a carboxyl group. An excess of Na2Cr207 acts as a buffer and favors smooth reaction. With 1.5 moles of Na2Cr207 the reaction occurs in accord with the equation ... 

Fieser and Seligman231 describe the preparation of a very stable ketimine. The Grignard reagent prepared from l-bromo-8-methylnaphthalene (66 g) and the equivalent of magnesium is mixed with 0-chlorobenzonitrile (26 g) in benzene and heated with stirring for 16 h under reflux. Then dilute hydrochloric acid is added and the o-chlorophenyl 8-methyl-l-naphthyl ketimine hydrochloride is filtered off and washed successively with cold water, alcohol, and ether. The yield amounts to 60 g. This ketimine is stable to hot hydrochloric acid of various concentrations. 

The alkyl halide may be replaced by an alkyl sulfate. For example, 1,2-di-methylnaphthalene is formed in 76% yield when 1 -bromo-2-methylnaphthalene is treated with lithium in ether and the product of this reaction is treated with dimethyl sulfate.319... 

Ring expansion of I-methylindenes. Gillespie et al have described a convenient synthesis of phenyl(tribromomethyl)mercury by mixing phenylmercuric chloride, sodium hydride, and bromoform in benzene with methanol as initiator. They have converted l-methyUndenes into 3-bromo-l-methylnaphthalenes by reaction with dibromocarbene generated from this precursor. Reaction of 1-methylindenes with dibromocarbene generated from bromoform with base... 

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