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Synlett 2004(15): 2739-2745  
DOI: 10.1055/s-2004-835630
LETTER
© Georg Thieme Verlag Stuttgart · New York

Esterification of Aldehydes and Alcohols with Pyridinium Hydrobromide Perbromide in Water

Shinsei Sayama*, Tetsuo Onami
Department of Chemistry, Fukushima Medical University, Hikariga-oka, Fukushima 960-1295, Japan
Fax: +81(24)5471369; e-Mail: ssayama@fmu.ac.jp;
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Publikationsverlauf

Received 31 August 2004
Publikationsdatum:
08. November 2004 (online)

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Abstract

The direct esterification of aldehydes and alcohols was carried out with pyridinium hydrobromide perbromide in water at room temperature. A variety of aldehydes were converted to respective ester derivatives with alcohols such as methanol, 1,2-ethanediol, 1,3-propanediol. Further, a variety of aliphatic alcohols were also converted to the corresponding Tishchenko-like dimeric esters in good yields under the same reaction conditions.

Key words

esterification - water - pyridinium hydrobromide perbromide - aldehyde - alcohol

4

4-Methylbenzoic acid was recovered in 88% yield at 2.0 molar equiv of PHPB and 16 molar equiv of ethylene glycol over 4-methylbenzoic acid in H2O for 14 h.

7

The oxidation of 2-ethyl-1,3-hexanediol (18) containing both secondary and primary hydroxyl groups, was carried out with 2.0 molar equiv of PHPB over 18 in H2O at r.t. for 75 h. Only the secondary 3-hydroxyl group of 18 was selectively oxidized to give hydroxyketone 19 in 82% yield (Table [6] , run 6).

8

Typical procedure for the Esterification of Iso butyraldehyde ( 4) and Dodecanol:
To a solution of PHPB (320 mg, 1.00 mmol) in H2O (8 mL) were added 4 (36 mg, 0.50 mmol) and dodecanol (93 mg, 0.50 mmol). After stirring for 14 h at r.t., the reaction mixture was treated with 0.5 M aq Na2S2O3 and extracted with EtOAc. The organic layer was washed with 0.5 M aq Na2S2O3, successively sat. aq NaCl, and dried over MgSO4. After removal of the solvent in vacuo, the residue was purified by column chromatography on silica gel (Wakogel C-200) with CCl4 and CHCl3 (3:1 v/v). Ester 4a (109 mg, 0.42 mmol) was obtained in 84% yield.

15

β-Phenylethylalcohol was recovered unchanged in 90% yield at a molar ratio of β-phenylethylalcohol, PHPB, pyridine (1:2:2) in H2O for 18 h.

21

Typical Procedure for the Dimeric Esterification of Dodecanol ( 12): To a solution of PHPB (160 mg, 0.50 mmol) in H2O (8 mL) was added 12 (46 mg, 0.25 mmol). After stirring for 13 h at r.t., the reaction mixture was treated with 0.5 M aq Na2S2O3 and extracted with EtOAc. The organic layer was washed with 0.5 M aq Na2S2O3, successively sat. aq NaCl, and_dried over MgSO4. After removal of the solvent in vacuo, the residue was purified by column chromatography on silica gel (Wakogel C-200) with CCl4. Dimeric ester 12a (44 mg, 0.12 mmol) was obtained in 95% yield.