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Synlett 2003(5): 0643-0646
DOI: 10.1055/s-2003-38377
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric Baeyer-Villiger Oxidation of Prochiral Cyclobutanones Using a Chiral Cationic Palladium(II) 2-(Phosphinophenyl)pyridine Complex as Catalyst

Katsuji Ito*a, Ayako Ishiia, Tomomi Kurodaa, Tsutomu Katsuki*b
a Department of Chemistry, Fukuoka University of Education, CREST, Japan Science and Technology (JST), Akama, Munakata, Fukuoka, 811-4192, Japan
Fax: +81(940)351367; e-Mail: itokat@fukuoka-edu.ac.jp;
b Department of Chemistry, Faculty of Science, Graduate School, Kyushu University 33, CREST, Japan Science and Technology (JST), Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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Publication History

Received 3 February 2003
Publication Date:
28 March 2003 (online)

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Abstract

Chiral cationic palladium(II) 2-(phosphinophenyl)pyridine (1a) complex was found to be an effective catalyst for asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones. For example, good and excellent enantioselectivities (80% and >99% ees) were achieved in the reactions of 3-phenylcyclobutanone and a tricyclic cyclobutanone, respectively.

Key words

asymmetric Baeyer-Villiger oxidation - asymmetric catalysis - palladium - chiral P-N ligand

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The geometrical problem is avoided, when a C 2-symmetric ligand is used.

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Typical experimental procedure To a solution of bis(benzonitrile)palladium(II) chloride (1.9 mg, 5.0 mol) in THF (0.4 mL) was added ligand 1a (2.3 mg, 5.5 mol) under nitrogen and stirred at room temperature for 1 h. Silver hexafluoroantimonate (3.4 mg, 10 mol) was placed another flask under nitrogen and to this flask was added the above palladium(II)-1a dichloride solution. After being stirred for 1 h at room temperature, the mixture was filtered through a pad of Celite under nitrogen. To the filtrate was added 3-phenylcyclobutanone (15.2 mg, 0.1 mmol) and then cooled to -60 °C. To the cooled solution was added UHP (12.2 mg, 0.13 mmol) and the mixture was further stirred at the temperature for 214 h. The mixture was concentrated and the residue was chromatographed on silica gel (hexane-EtOAc, 9:1) to give dihydro-4-phenylfuran-2(3H)-one (14.8 mg, 91%). The enantiomeric excess of the product was determined to be 80% ee by HPLC analysis using chiral stationary phase column (Daicel Chiralpak AD-H; hexane-i-PrOH, 95:5).