Synlett 2010(7): 1115-1117  
DOI: 10.1055/s-0029-1219795
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Organocatalytic Mitsunobu Reactions with 3,5-Dinitrobenzoic Acid

Tracy Yuen Sze But, Jinni Lu, Patrick H. Toy*
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. of China
Fax: +852 28571586; e-Mail: phtoy@hku.hk;
Further Information

Publication History

Received 4 February 2010
Publication Date:
23 March 2010 (online)

Abstract

A second generation procedure for organocatalytic ­Mitsunobu reactions using 3,5-dinitrobenzoic acid as the pro-­nucleophile has been developed. The increased acidity of this acid compared to 4-nitrobenzoic acid, which was used in the original procedure, allowed for higher isolated yields of the desired products and eliminated formation of undesired acetate byproducts.

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General Procedure for Catalytic Mitsunobu Reactions: To a solution of 10 (1.98 mmol) and the alcohol substrate (1.8 mmol) in anhydrous THF (11 mL) under a N2 atmosphere, was added 2 (0.028 mL, 0.18 mmol) and 8 (1.16 g, 3.6 mmol). This was followed by the addition of a solution of 1 (0.94 g, 3.6 mmol) in anhydrous THF (4 mL) slowly by syringe pump (0.25 equiv/h). The reaction mixture was stirred for a total of 16 h and then was diluted with Et2O (30 mL). The organic phase was separated and then washed sequentially with sat. aq NaHCO3 (2 × 20 mL), and brine (20 mL), dried with Na2SO4, filtered and concentrated in vacuo. The crude product was purified by column chromatography. All ester products were characterized by ¹H and ¹³C NMR spectroscopy. Enantiomeric excesses were determined by HPLC. See Supporting Information for details