Propanal → HCID 11389404, compound

Participants

Reaction Steps

A solution of freshly distilled propionaldehyde (1.81 mL, 25.0 mmol) in 12.5 mL dimethylformamide pre-cooled to 4° C. was added slowly over the course of 20 h to a stirring suspension of isobutyraldehyde (4.54 mL, 50 mmol), L-proline (288 mg, 2.5 mmol) and 12.5 mL dimethylformamide at 4° C. After 30 h, the resulting solution was diluted with diethyl ether and washed successively with water and brine. The combined aqueous layers were back-extracted with 3 portions of dichloromethane. The organic layers were combined, dried over anhydrous MgSO4, and concentrated in vacuo. Flash chromatography (20:7 pentane:diethyl ether) afforded the title compound as a clear, colorless oil in 82% yield (2.65 g, 20.6 mmol), >99% ee and 96:4 anti:syn. Analytical data for this compound are identical in every respect to the previously reported values (Mahrwald, supra), with the exception of optical rotation which has not been reported. [α]D=−17.9 (c=1.0, CHCl3). The product ratios were determined by GLC analysis of the acetal derived from 2,2-dimethylpropane-1,3-diol (obtained by the method of Yamamoto) using a Bodman Chiraldex β-DM (30 m×0.25 mm) column (110° C. isotherm, 23 psi); (2S, 3S) anti isomer tr=31.8 min, (2R, 3R) anti isomer tr=33.9 min, (2R, 3S) and (2S, 3R) syn isomers tr=29.4, 29.8 min.

Provenance & Evidence