A Catalytic System for the Activation of Diorganozinc Reagents

Abstract

We report a novel catalytic system for the activation of diorganozinc reagents. We assumed that the nucleophilic activation of diethylzinc should be efficiently performed by simple alkali metal salts. Indeed, the combination of sodium salts and 15‐crown‐5 significantly accelerates the rate of diethylzinc addition to benzaldehyde under mild conditions. The activity of the catalytic system strongly depends on the nature of the anion, decreasing in the order I– > Br– > Cl– > F–. Under the optimized reaction conditions, various aryl, hetero aryl, and aliphatic aldehydes were converted with diethylzinc and the corresponding product was obtained in excellent yields. The first X‐ray absorption spectroscopy measurements on such type of reactions provide initial insights that support the proposed catalytic cycle and suggest the formation of a zincate complex.

Green synthesis of (S)‐1‐(furan‐2‐yl)propan‐1‐ol from asymmetric bioreduction of 1‐(furan‐2‐yl)propan‐1‐one using whole‐cell of Lactobacillus paracasei BD101

“…2.5 | (S)-1-(furan-2-yl)propan-1-ol ((S)-2) 19 Pale yellow oil, isolated yield 96%, 1 H NMR (400 MHz, CDCl 3 ) δ = 7.37-7.35 (m, 1H), 6.33-6.30 (m, 1H), 6.24-6.22 (m, 1H), 4.60 (t, J = 6.7 Hz, 1H), 1.92-1.84 (m, 2H), 0.96 (t, J = 7.4 Hz, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ = 156.9, 142.1, 110.3, 106.0, 69.5, 28.9, 10.1; [α] D 22 = À19.6 (c 1.75, CHCl 3 ), ee > 99%; [Lit.…”

Chemo- and Enantioselective Addition and β-Hydrogen Transfer Reduction of Carbonyl Compounds with Diethylzinc Reagent in One Pot Catalyzed by a Single Chiral Organometallic Catalyst

“…By increasing the use of the diethylzinc reagent, the addition product was obtained with almost the same level of yield and ee , but the enantioselectivity of the reduction product decreased significantly (Table , entry 2). For the asymmetric ethylation reaction, the addition reaction between benzylaldehyde and the diethylzinc reagent is very slow in the absence of the chiral ligand. − However, for the asymmetric β-hydrogen transfer reduction, the diethylzinc reagent can reduce the α-trifluoromethyl ketone without the chiral ligand. − Therefore, an excessive amount of the diethylzinc reagent has a great influence on the enantioselectivity of the asymmetric β-hydrogen transfer reduction while it has little effect on the asymmetric ethylation. When 2.0 equiv of the diethylzinc reagent was used, the yield of the reduction product was only 67% with 65% ee (Table , entry 3).…”