Anisole, bromination iodination

This method has also been used for the iodination of phenols and for the bromination of anisole to give 4-bromoanisole (87%), of 1,3-dimethoxybenzene to give 4-bromo-L3-dimethoxybenzene (80%). 

To a stirred solution of 7.6 g of 3-ethoxy-2-(methylthio)anisole in 100 mL CH2CI2 there was added 6.2 g elemental bromine dissolved in 50 mL CH2CI2. The initial dark red color gradually faded to a pale yellow and there was a steady evolution of HBr. An added crystal of iodine did not appear to increase the rate of reaction. After 4 min the color was a pale orange. The reaction mixture was extracted with H20 containing sufficient dithionite to remove most of the residual color. The solvent was removed under vacuum leaving 12.2 g of a pale yellow fluid oil. This was distilled at 100-110 deg C at 0.3 mm/Hg to yield a mixture of 4-bromo-3-ethoxy-2-(methylthio)anisole and 6-bromo-3-ethoxy-2-(methylthio)anisole as a pale yellow, highly... 

The work on isotope eifects in the iodination of p-nitrophenol, and on the bromination and bromodesulphonation of anisole-4-sulphonic acid not only excludes mechanisms (10-11), (12-13) and (14-15), but also shows that the mechanism (6-2) does not involve a rapid and reversible first step and a slow proton transfer, but a typical steady-state intermediate ( iPa]... 

Only a few examples of oxidative brominations utilizing hypervalent iodine(III) reagents have been reported. Stable bromobenziodoxoles (Section 2.1.8.1.1) have been demonstrated to be active brominating agents. In particular, benziodoxole 85 can be used for selective allylic and benzylic brominations under radical conditions [89] and bromobenziodoxole 86 has been utilized for electrophilic bromination of anisole or bromolactonization of 4-pentenoic acid (Scheme 3.32) [90]. 

Tetrahydrofuran treated a few min. with diborane and iodine at room temp, and the intermediate boric acid ester treated with water 4-iodobutan-l-ol. Y 90%. — Similarly Anisole phenol. 1 mole diborane cleaves 6 moles ether. Large excesses of reagents are unnecessary and should be avoided. Metal boron hydrides are comparable in reactivity to diborane. Bromine and interhalogen compounds such as iodine chloride react more vigorously but are in general less convenient. L. H. Long and G. F. Freeguard, Nature 207, 403 (1965). 

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