I apologize if this has already come up on here, I did use the f'ing search engine..
It seems that m-haloanisoles can be prepared from m-halonitrobenzenes consistently in very good yields. The rxn is similar to the copper-catalysed nucleophilic displacement of halogens by alkali methoxide. The halonitrobenzene is denitrated and the nitro group replaced by the methoxide ion, yielding the m-haloanisoles.
The difference here is the ease of performing this synth. In the reference, the alkali methoxide is not always employed at the beginning of the synth, it can actually be generated in situ!
All that is required is the alkali hydroxide salt (KOH or NaOH, potassium gives higher yields), a PTC and methanol in just about any non-polar solvent. At first they try it under N2 but find that it leads to the formation of some byproducts and only modest yields. So they perform it with oxygen blowing thru the mixture and obtain consistent 83%+ yields in only 2.5-3 hrs at 50-60deg C, although I doubt the oxygen is really necessary.. Using KOH to prepare the methoxide in situ, they prepare 3-bromoanisole in 84% yield. bromo, chloro, and trimethylfluoronitrobenzenes all give yields this high.. m-iodonitrobenzene does not work very well thou.. only 52% conversion after 24hrs..
Even the PTC is not entirely necessary, in the abscence of a PTC they still obtain a 53.7% conversion w/in situ KOMe.
Here is the ref:
One-Step Preparation of Some 3-Substituted Anisoles, Organic Process Research & Development 2003, 7, 303-305;
.. and here's the detailed procedure, enjoy:
Representative Procedure for the Preparation of 3-Chloroanisole, 2b, Using Solid Sodium Methoxide.
The reaction is carried out with the forced passage of air through the reaction solution. To a solution of 3-chloronitrobenzene, 1b, (47.3 g, 0.3 mol) in toluene (60 mL) are added at room temperature NaOMe powder (19.4 g, 0.36 mol), solid KOH powder (33.6 g, 0.51 mol), and tetrabutylammonium bromide (12.3 g, 0.038 mol). The heterogeneous mixture is stirred vigorously at 50 °C for 2 h. The mixture is then cooled and washed with water to remove inorganic compounds, followed by phase separation. The organic phase is washed with aqueous HCl solution to remove tetrabutylammonium bromide and products of its decomposition remaining after the washing with water. The organic phase is distilled under vacuum to afford a final pure anisole, 2b, (88 °C, 18 mmHg) as a colourless, clear liquid (35.9 g, 84%). The same procedure is employed when the solid NaOMe is replaced by solid KOMe.
Representative Procedure for the Preparation of 3-Bromoanisole, 2a, Using Potassium Methoxide Prepared in Situ.
The reaction is carried out with the forced passage of air through the reaction solution. A heterogeneous mixture of cyclohexane (210 mL), methanol (38.4 g, 1.2 mol), solid KOH (158.1 g, 2.4 mol), and tetrabutylammonium chloride (50.5 g, 0.18 mol) is stirred vigorously at 55 °C for about 5 min. A solution of 3-bromonitrobenzene, 1a, (202 g, 1 mol) in cyclohexane (110 mL) is added dropwise at 55 °C over 0.5 h. The heterogeneous reaction mixture is stirred at 60 °C for 2.5 h. The mixture is treated in a manner similar to that described above for anisole, 2b. The organic phase is distilled to afford a final pure anisole, 2a, (92-93 °C, 14 mmHg) as a colorless, clear liquid (155 g, 83%). The products, 2a-c, were identified by 1H NMR and mass spectroscopy. All the spectral data obtained were compared with those of authentic samples. The anisoles, 2d,e, the byproducts, 3a,b,e, 4a,b, 5, 6, as well as the phenetols, 7a,b, were identified by mass spectroscopy.
Scale-Up Batch.
Batch preparations of 3-bromoanisole, 2a, in toluene using KOMe prepared in situ and tetrabutyammonium bromide as a catalyst, were performed in a 250-L reactor under the conditions described in the Experimental Section for the laboratory synthesis of 2a. The toluene was repeatedly recycled. The average isolated yield of 2a was 85%, based on 1a. The hazardous, aqueous waste containing potassium nitrite (7-10% w/w) underwent a special treatment based on the reduction of nitrites to nitrogen by urea or sulfamic acid. This waste treatment is rapid, environmentally acceptable, and inexpensive.
Oh, and as for our use for this little gem, need I mention the two compounds in Dr. Shulgin's book that have a bromine atom meta to a methoxy?