It may be done with phosphorus tribromide in DMF.

Hello,

one problem could be the low solubility of long-chain alcohols in common solvents...

In addition to the methods from John one can also use this way:

1.) transformation of alcohol into the THP-ether using 3,4-dihydropyran, CH2Cl2 and catalytic amounts of pyridinium p-toluenesulfonat (PPTS) 18h at room temp. and

2.) bromination of THP-group with PPh3, Br2 in CH2Cl2 at room temp. (according to a procedure described by Schwarz et al. JOC, 1975, 2410)

Yields after purification (chromatography) >90%.

Regards.

PS: One can also use the mesyl-group instead of the tosyl-derivative; prepared in CHCl3 with TEA as base, followed by reflux with LiBr in dry (!) acetone.

Dear John,

please have a look at Mori et al. Tetrahedron 1972, 28, 3739.

We use this mesylate-LiBr-way for, e.g., conversion of long-chain hydroxy carboxylic acid methylesters into the corresponding bromo-derivatives (see Chem. Eur. J. 2007, 13, 5300.)

Regards.

Dear John,

unfortunately, there is no supporting information, because the conversion of OH to Br using mesylate-LiBr is a very 'old' reaction and we followed the route described by Mori et al. Tetrahedron, 1972... I think, Mori used tosylchloride and pyridine as base, but, we got some trouble with purification so we used mesylchloride and TEA in CHCl3 and it worked quite well. The important point for subsequent substitution with LiBr in acetone is that all components have to be free from traces of water, particularly the mesylate.

For the procedure: try a 2-3fold excess of LiBr with respect to the mesylate/tosylate in a medium amount of acetone - but not to much acetone - and reflux for, say, 12h.

Good Luck!

Simon.

Dear Aman.

Try N-bromosuccinimde with triphenyl phosphine in toluene with gentle heating approximately 90 C. the purification can be achieve simply by dissolve the crude in ether so the triphenyl phosphine and triphenyl phosphine oxide can be crystallize and remove by filteration . repeat the purification several time to get a pure bromide product.