[haoyuforever]

Hi,
I need to synthesize a monobenzyl sebacate half ester precursor which is HO-(C=O)-(CH2)8-(C=O)-O-Bn.
I followed a procedure used to synthesize monobenzyl adipate using dicarboxylic acid with benzyl alcohol (in excess, 1.5 eq) in toluene in the presence of strong acid catalyst. It worked great.

But here is the problem. After the work-up (I used NaOH solution to adjust the pH to 9 to remove diester which is in toluene and then bring pH back to 2 to remove diacid which is in the aqueous layer), I found substantial amount of sebacic acid presented in the final products by integration of NMR spectrum. I thought the NaOH addtion might hydrolyze the ester, then I switched to 1M NaHCO3, but surprisingly, what I only had is sebacic acid in the final ether layer and benzyl substituted product was still in the toluene layer before acidify the solution.

Does anyone have any idea of how to get the pure product or is there any better way to synthesize this compound?

Thanks for help,

[mickelcorleone]

ok see this article

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http://www.organic-synthesis.co.cc/?p=250