Benzaldehyde → Stilbene oxide

Beteiligte Stoffe

Reaktionsschritte

To a rapidly stirred solution of a sulphide of formula (D) wherein Ra is CH2OCH3 and Rb is H (1 equivalent, 80 mg, 0.33 mmol), rhodium (II) acetate dimer (1 mol %, 1.5 mg, 0.003 mmol), benzyltriethylammonium chloride (20 mol %, 15 mg, 0.066 mmol) and benzaldehyde (35 mg, 0.33 mmol) in anhydrous acetonitrile (1 cm3) was added the tosyl hydrazone salt (1.5 equivalents, 147 mg, 0.495 mmol). The heterogeneous mixture was stirred rapidly at room temperature to facilitate even dispersion of the solid, then held at 30° C. (bath temperature) for 32 hours. The mixture was then cooled and ethyl acetate/water (0.5 cm3+0.5 cm3) added. The organic phase was removed and the aqueous phase extracted with ethyl acetate (2×0.5 cm3). The combined organic extracts were then dried over sodium sulphate, filtered and concentrated in vacuo. The residue was purified on silica, eluting with 0-25% DCM/petrol, to give stilbene oxide as a white solid (38 mg, 59%) and as a >98:2 mixture (trans:cis) of diastereoisomers; enantiomeric excess 93% (R, R major) as determined by chiral HPLC (see conditions below). The NMR data for this compound is reported above.

Herkunft & Nachweise