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Synlett 2010(20): 3089-3091  
DOI: 10.1055/s-0030-1259043
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Rhenium Complex as a Useful Catalyst for Acylative Cleavage of Ethers

Rui Umeda, Kenta Kaiba, Toshimasa Tanaka, Yuuki Takahashi, Takashi Nishimura, Yutaka Nishiyama*
Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
Fax: +81(6)63394026; e-Mail: nishiya@kansai-u.ac.jp;
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Publication History

Received 15 September 2010
Publication Date:
17 November 2010 (online)

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Abstract

It was found that a rhenium complex such as ReBr(CO)5 acts as an efficient catalyst for the acylative cleavage of the carbon-oxygen bond of ethers with acyl chloride, giving the corresponding esters in moderate to good yields.

Key words

rhenium complex - ethers - acylation - esters - catalysis

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It was found that Lewis acids,³ group 5 or 6 metal complexs,4 metals such as Al5 and Zn,6 and iodine7 can be used as a useful catalyst for the transformation. However, many of these methods involve some disadvantages (i) the use of toxic, expensive, and unstable agents, (ii) the formation of mixtures of products, (iii) low yields, and (iv) limitation of the substrates.

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We also investigated the reaction of 1a and 2a using other rhenium complexes as a catalyst. The yields of ester 3aa were in slightly lower compared to that of ReBr(CO)5 (90%), Re2(CO)10 (71%), MeReO3 (84%), ReCl5 (74%), and Re2O7 (80%).

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General Procedure A DCE (3.0 mL) solution of acyl chloride (0.6 mmol), ether (0.5 mmol), and ReBr(CO)5 (2.5 mol%) was stirred under an atmosphere of nitrogen at 80 ˚C for 2 h. After the reaction was completed, H2O was added to the reaction mixture and extracted with EtOAc. The organic layer was dried with MgSO4. The resulting mixture was filtered, and the filtrate was concentrated. Purification of the residue by silica gel column chromatography afforded ester. The structures of the products were assigned by their ¹H NMR, ¹³C NMR, and mass spectra.