Communications
DOI: 10.1002/anie.200705932
Asymmetic Catalysis
Chiral Brønsted Acid Catalyzed Asymmetric Baeyer–Villiger Reaction
of 3-Substituted Cyclobutanones by Using Aqueous H O **
2
2
Senmiao Xu, Zheng Wang, Xue Zhang, Xumu Zhang, and Kuiling Ding*
The Baeyer–Villiger (BV) reaction represents one of the most
well-known and widely applied reactions in organic syn-
The research was inspired by the fact that BV reaction is
accelerated by strong Bønsted acids, and that the activity of
[
1]
thesis. Although more than one century has gone by since its
the peracid is dependent on the acidity of the Bønsted
[
2]
[3,11]
discovery in 1899, the BV reaction is still far from being fully
developed. Although the use of aqueous hydrogen peroxide
as an environmentally benign oxidant has been a long-sought
acid.
It was reported that the use of a stoichiometric
amount of the chiral organic hydroperoxide {(4R,5R)-5-
[(hydroperoxydiphenyl)methyl]-2,2-dimethyl-1,3-dioxolan-4-
yl}diphenylmethanol (TADOOH) afforded enantioselectivi-
[
3]
goal for the BV reaction, significant efforts still need to be
made in the area of enantioselective BV reactions. Since the
ties of 55% in the asymmetric BV oxidation of bicyclo-
[
4a]
[4b]
[12]
pioneering work by the groups of Strukul and Bolm in
994, a number of chiral metal complexes or organic
molecules have been developed as promoters or catalysts
[4.2.0]octanone.
The difficulty in developing a catalytic
1
enantioselective version of this reaction may be ascribed to
the weak acidity of the hydroxy groups in the a,a,a’,a’-
tetraaryl-1,3-dioxolan-4,5-dimethanol (TADDOL) molecule.
Chiral phosphoric acids derived from 2,2’-dihydroxy-1,1’-
binapthyl (binol) are recognized as Brønsted acids that are
widely used as catalysts in a variety of asymmetric reactions
[
5]
for the BV reaction of various ketones, but there are only a
few cases in which the catalysts are used in combination with
[4a,6]
aqueous hydrogen peroxide as the oxidant.
Although very
impressive results have been achieved for the catalytic
enantioselective BV reaction in the work reported by the
[13]
with high catalytic activity and excellent enantioselectivity.
[
4b,7]
[8]
[6b]
groups of Bolm,
opment of the reaction is slow when compared to the rapid
Katsuki, and Murahashi, the devel-
A preliminary examination of binol-derived phosphoric acid
1a (10 mol%) in the BV oxidation of 3-phenylcyclobutanone
(2a) with 1.5 equivalents of aqueous H O (30%) in CHCl at
[9]
development of other catalytic asymmetric transformations.
2
2
3
To the best of our knowledge only a few catalyst systems
afford products from the BV oxidation of 3-substituted
room temperature afforded 3-phenyl-g-butyrolactone (3a)
with good catalytic activity (12 h, 99% yield), albeit very poor
enantioselectivity (ca. 2% ee). Notably, a reaction did not
occur in the absence of 1a under otherwise identical
experimental conditions. These results clearly showed the
accelerating effect of the phosphoric acid in the BV oxidation
of cyclobutanone and prompted us to improve the catalytic
performance of the phosphoric acids by tuning the steric and
electronic properties of 3,3’ substituents and the backbone of
the scaffold (Figure 1). Both the catalytic efficiency and
asymmetric induction are strongly dependent on the solvents
used. Among the variety of solvents examined for the
[
8b,c]
cyclobutanones in more than 80% ee,
despite the fact
that some enzymatic systems show excellent enantiocontrol in
[10]
the reaction.
Herein, we communicate our preliminary
results on the first example of the enantioselective BV
oxidation of 3-substituted cyclobutanones catalyzed by a
chiral Brønsted acid and 30% aqueous H O as the oxidant to
2
2
afford the corresponding g-lactones in excellent yields and up
to 93% ee.
[
*] S. Xu, Dr. Z. Wang, Dr. X. Zhang, Prof. Dr. K. Ding
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
354 Fenglin Road, Shanghai 200032 (P.R. China)
Fax: (+86)21-6416-6128
E-mail: kding@mail.sioc.ac.cn
Prof. Dr. X. Zhang
Department of Chemistry and Chemical Biology
Center of Molecular Catalysis
Rutgers, The State University of New Jersey
610 Taylor, Piscataway, New Jersey 08854 (USA)
[
**] Financial support from the National Natural Science Foundation of
China (No.20532050, 20423001), the Chinese Academy of Sciences,
the Major Basic Research Development Program of China (Grant
No. 2006CB806106), the Science and Technology Commission of
Shanghai Municipality, and Merck Research Laboratories is grate-
fully acknowledged.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Figure 1. Binol- and H -binol-derived phosphoric acids 1a–r.
8
2
840
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 2840 –2843