Acetaldehyde → (-)-Ipsenol

Participants

Reaction Conditions

Reaction Steps

Isovaleraldehyde (2.15 g, 2.68 mL, 25 mmol) in ether (6 mL) was added dropwise to a rapidly stirred solution of B-Isoprenyldiisopinocampheylborane, dIpc2BIpn, maintained in THF/EE (1:2) at -100° C. Stirring was continued for 6 h, when the 11B NMR spectrum of an aliquot showed a peak at δ52 ppm, corresponding to a borinate indicating completion of the reaction. The reaction mixture was warmed to 0° C. and acetaldehyde (2.1 mL, 37.5 mmol) was added when one equiv of α-pinene was eliminated. 11B NMR showed a peak at δ32 ppm corresponding to a boronate. The solvents were removed in vacuo and EE (20 mL) was added, followed by 1.1 equiv. of diethanolamine (2.6 mL, 27.5 mmol). Stirring was continued for 2 h and the precipitated boron components were filtered and the filtrate concentrated. Distillation (92°-94° C./19 mm Hg) provided 2.3 g (60 %) of (+)-ipsenol, [α]D =+18.5° which corresponds to 100% ee. The spectral properties were identical to the sample obtained from example 9.

Provenance & Evidence