Benzaldehyde → (R)-(+)-1-Phenyl-1-propanol

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Reaction Steps

Reaction of benzaldehyde with diethylzinc in the presence of the polymer of Example 1 to give (R)-1-phenyl-1-propanol. The polymer of Example 1 (28 mg, 0.05 mmol based on the 2,2'-substituted biphenyl subunit) and diethylzinc (0.14 mL, 1.3 mmol) were added to a Schlenk flask containing toluene (10 mL) (dried with Na and degassed with N2), under N2 and at room temperature, to form an organozinc species. After ca. 15 min, the flask was cooled to 0° C. and benzaldehyde (0.1 mL, 1 mmol) was added in a dropwise manner. Stirring was continued at this temperature for 10 h. The 1H NMR spectrum of the crude mixture showed 100% conversion with no side product. The reaction was then quenched at 0° C. with the addition of 1N HCl and the aqueous layer was extracted with diethyl ether. The combined organic layer was washed with brine until pH 7 and then dried over anhydrous Na2SO4. Concentration in vacuum gave a pale yellow oil, which upon treatment with MeOH (20 mL) precipitated the polymer. The filtrate was concentrated and purified by column chromatography on silica gel (eluent: EtOAc/hexanes 1/4) to afford (R)-1-phenyl-1-propanol as a colorless liquid (122 mg, 89%). 1H NMR (270 MHz, CDCl3) δ 0.91 (t, J=7.4, 3H), 1.78 (dq, J=7.3, 6.4, 2H), 1.89 (br, 1H), 4.58 (t, J=6.5, 1H), 7.25-7.37 (m, 5H) . [α]D =42.91 (c=2.44, CHCl3). The ee value was determined to be 92.2% on GC with a chiral column (β-Dex capillary column, Supelco Company). The recycled catalyst showed the similar reactivity and the same ee for the product.

Provenance & Evidence