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Synlett 2004(13): 2307-2310  
DOI: 10.1055/s-2004-832812
LETTER
© Georg Thieme Verlag Stuttgart · New York

Silica Gel-Supported Polyphosphoric Acid (PPA/SiO2) as an Efficient and Reusable Catalyst for Conversion of Carbonyl Compounds into Oxathioacetals and Dithioacetals

Tadashi Aoyama*a, Toshio Takidoa, Mitsuo Kodomarib
a Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan
b Department of Applied Chemistry, Shibaura Institute of Technology, Shibaura, Minato-ku, Tokyo 108-8548, Japan
Fax: +81(3)32590818; e-Mail: aoyama@chem.cst.nihon-u.ac.jp;
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Publication History

Received 30 June 2004
Publication Date:
08 September 2004 (online)

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Abstract

A simple and efficient method for the conversion of carbonyl compounds to oxathioacetals and dithioacetals by using polyphosphoric acid supported on silica gel (PPA/SiO2) as an acid catalyst have been developed. PPA/SiO2 is easily recovered from the reaction mixture and reused without a decrease in catalytic ­activity.

Key words

oxathioacetals - dithioacetals - protecting groups - polyphsphoric acid - silica gel

18

The Preparation of PPA/SiO 2 : PPA (2.1 g) was charged in the round-bottom flask, and CHCl3 (100 mL) was added. After the mixture was stirred at 50 ºC for 1 h, SiO2 [Wakogel C-200 (Wako Pure Chemical Ind. Ltd.), 4.9 g] was added to the solution, and the mixture was stirred for another 1 h. The CHCl3 was removed with rotary evaporator and the resulting solid was dried in vacuo at r.t. for 3 h.

19

Used PPA/SiO2 was regenerated as follows: PPA/SiO2 was recovered by filtration from the reaction mixture, and then it was put in the 50 mL round-bottom flask and dried in vacuo at 100 °C for 2 h.