A Catalyst for Asymmetric Baylis-Hillman Reaction

A cinchona alkaloid, β-isocupreidine (1), is an effective catalyst in the asymmetric Baylis-Hillman reaction. The reaction with aldehydes and 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA) by the use of the catalyst 1 (0.1 eq.) gives the corresponding adducts with high enantioselectivity.¹⁾

β-Isocupreidine (1) also catalyzes the asymmetric aza-Baylis-Hillman reaction.²⁾

Typical Procedure: Synthesis of 2¹⁾
To the solution of benzaldehyde (1.0 mmol) and β-isocupreidine (1, 0.1 mmol) in DMF (1 mL) at −55 °C was added HFIPA (1.3 mmol). After stirring at −55 °C for 48 h, the reaction was quenched with 0.1 M HCl (3 mL). The reaction mixture was extracted with EtOAc, washed with saturated NaHCO₃ and brine, dried over MgSO₄, concentrated, and chromatographed on silica gel (hexane-EtOAc) to give 2 (Y. 75%, 97% ee).

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It was reported that the reaction yield would decrease by using 1 that absorbed moisture in the air. We have taken all measures to avoid moisture during manufacturing and shipping. If the reaction result is not desirable, a good result may be obtained after dissolving 1 into tetrahydrofuran followed by azeotropic removal of water under reduced pressure.