C O M M U N I C A T I O N S
Table 2. NHC-Catalyzed Hydroacylation of Unactivated Double
Acknowledgment. We thank Ms. Karin Gottschalk, Dr. Klaus
Bergander, Dr. Sascha Nowak, and Prof. Uwe Karst for support
and Prof. Jeffrey Bode and Prof. Armido Studer for helpful
discussions. Generous financial support by the DFG and fellowships
by the DAAD (K.H.), Alexander von Humboldt Foundation
(A.T.B.), and the International NRW Graduate School of Chemistry
(I.P.) are gratefully acknowledged. The research of F.G. has been
supported by the Alfried Krupp Prize for Young University
Teachers of the Alfried Krupp von Bohlen und Halbach Foundation.
a
Bonds: Variation of the Aromatic Ring
Supporting Information Available: Experimental and characteriza-
tion details. This material is available free of charge via the Internet at
References
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a General conditions: 1 (1.0 mmol), 3 (20 mol %), DBU (40 mol %),
1,4-dioxane (2.0 mL), 120 °C, and 2 h. Given are isolated yields. b 24 h.
c 0.40 mmol scale. d 3 h. e Using 10 mol % of 3, an isolated yield of
91% was obtained. f 0.32 mmol scale. g 6 h. h 0.69 mmol scale, 132 h.
chroman-4-ones and demonstrates an unprecedented reactivity of
the catalytically generated acyl anion equivalent. Efforts to obtain
further insight into the mechanism and the development of an
asymmetric variant are ongoing.
Table 3. Variation of the Allyl Moietya
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entry
R1
R2
product
yield of 9 (%)b
1
2
3
4
5
6
H
H
CH3
Ph
H
H
H
9a
9b
9c
9d
9e
9f
<5
25
(7) See Supporting Information for further details.
CH2CH3
<5
(8) Lebeuf, R.; Hirano, K.; Glorius, F. Org. Lett. 2008, 10, 4243.
(9) Trost, B. M.; Jiang, C. Synthesis 2006, 369.
(10) Breslow, R. J. Am. Chem. Soc. 1958, 80, 3719.
(11) For a recent example and key references on the Conia-ene reaction, see:
Corkey, B. K.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 17168. In our
reaction, the NHC might generate a 1,3-enophile undergoing a concerted
Conia-ene-type reaction. Despite different transition-state geometries of the
Conia-ene and our reaction (six- vs five-membered, respectively), the overall
similarity, including the polarity of the reacting olefins, is striking.
CH2OCH2Ph
CH2OCH2CHdCH2
CH2OCH2C′CCH2CH3
93c
89c
83c
H
a General conditions: 8 (1.0 mmol), 3 (20 mol %), DBU (40 mol %),
1,4-dioxane (2.0 mL), 120 °C, 2 h. b Isolated yield. c 24 h.
Scheme 1. Formation of All-Carbon Quaternary Stereocenters
(12) ICP-OES (inductively coupled plasma optical emission spectrometry)
analyses were performed determining the amount of transition-metal
impurities in the reaction mixture. No significant amounts of any transition-
metal contaminant were detected.7
JA906361G
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