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Useful Cinchona Alkaloid Derived Catalysts
No.162(July 2014)
A cinchona alkaloid derivative, β-isocupreidine (β-ICD, 1), has been known as a catalyst which catalyzes reactions such as the Morita–Baylis–Hillman (MBH) reaction1), aza-MBH reaction2), Michael reaction3), electrophilic amination4), and [2+2] cycloaddition5,6) with high enantioselectivities. Recently, Hatakeyama, Ishihara, et al. have developed α-isocupreine (α-ICPN, 2), a pseudoenantiomer of 1, and reported the MBH reaction using 2.7) According to their results, in the reaction of various aldehydes with 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA), the catalyst 1 affords (R)-products, and the catalyst 2 affords the related (S)-isomers respectively, in good yields. Thus, both enantiomers can be obtained in various kinds of asymmetric reactions by using these two catalysts properly. This synthetic method has broad applicability to the synthesis of natural products.
Typical Procedure:
1 or 2 (0.1 or 0.2 mmol) is dissolved in THF (2 mL) and the solution is evaporated by rotary evaporation at room temperature. After repeating this operation three times, the amorphous residue is dried under vacuum at room temperature for 10 min. A solution of the dried 1 or 2 and aldehyde (1.0 mmol) in DMF is cooled to –55 °C, and HFIPA (1.3 mmol) is then added. After the mixture is stirred at –55 °C, the reaction is quenched by the addition of 0.1 M HCl (3 mL). The mixture is extracted with EtOAc, washed with saturated NaHCO3 and brine, dried over MgSO4, concentrated, and chromatographed on silica gel (hexane-EtOAc) to give the corresponding products.
1 or 2 (0.1 or 0.2 mmol) is dissolved in THF (2 mL) and the solution is evaporated by rotary evaporation at room temperature. After repeating this operation three times, the amorphous residue is dried under vacuum at room temperature for 10 min. A solution of the dried 1 or 2 and aldehyde (1.0 mmol) in DMF is cooled to –55 °C, and HFIPA (1.3 mmol) is then added. After the mixture is stirred at –55 °C, the reaction is quenched by the addition of 0.1 M HCl (3 mL). The mixture is extracted with EtOAc, washed with saturated NaHCO3 and brine, dried over MgSO4, concentrated, and chromatographed on silica gel (hexane-EtOAc) to give the corresponding products.
References
- 1) β-Isocupreidine-catalyzed asymmetric Baylis–Hillman reactions
- 2) β-Isocupreidine-catalyzed asymmetric Baylis−Hillman reaction of imines
- 3) Stereocontrolled creation of adjacent quaternary and tertiary stereocenters by a catalytic conjugate addition
- 4) Asymmetric construction of quaternary stereocenters by direct organocatalytic amination of α-substituted α-cyanoacetates and β-dicarbonyl compounds
- 5) Intramolecular, nucleophile-catalyzed aldol-lactonization (NCAL) reactions: Catalytic, asymmetric synthesis of bicyclic β-lactones
- 6) Organocatalyzed formal [2 + 2] cycloaddition of ketimines with allenoates: Facile access to azetidines with a chiral tetrasubstituted carbon stereogenic center
- 7) α-Isocupreine, an enantiocomplementary catalyst of β-isocupreidine
- a) Y. Nakamoto, F. Urabe, K. Takahashi, J. Ishihara, S. Hatakeyama, Chem. Eur. J. 2013, 19, 12653.
- b) S. Hatakeyama, J. Ishihara, K. Takahashi, Y. Nakamoto, Nagasaki University, Jpn. Kokai Tokkyo Koho 2013 227272, 2013.
- a) Y. Nakamoto, F. Urabe, K. Takahashi, J. Ishihara, S. Hatakeyama, Chem. Eur. J. 2013, 19, 12653.
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