Styrene Oxide → (+)-Styrene oxide

Participants

Reaction Steps

A 500-mL flask, equipped with a temperature probe, a mechanical stirrer, a vacuum adapter, and a dip tube, was charged with (R,R)-Co(salen) (6.57 g, 0.0109 mol, 0.63 mol %), styrene oxide (209.0 g, 199.0 mL, 1.74 mol), and water (5.0 g, 5.0 mL, 0.28 mol, 16 mol %). A slight vacuum was applied to the flask to draw air into the reaction mixture through the dip tube (subsurface), agitation was initiated, and p-nitrobenzoic acid (3.64 g, 0.0218 mol, 1.25 mol %) was added in one portion. An exotherm was noted that ceased after about 3 h. When the internal temperature remained constant, additional water (5.0 g, 5.0 mL, 0.28 mol, 16 mol %) was added. An exotherm was again observed that ceased after about 1 h. This cycle was repeated two more times (2×5.0 g water). A final portion of water (42.6 g, 42.6 mL, 2.37 mol, 136 mol %) was added after the last exotherm had ceased. After stirring a total of 24 h, the reaction was deemed complete by HPLC. The reaction mixture was a brown solution with suspended orange solids. Ammonium hydroxide (3.0 mL, 28%, 0.049 mol, 2.8 mol %) was added, and the reaction mixture was stirred at room temperature for 2 h. A dark brown solution was obtained. Air flow through the reaction mixture was stopped, and the reaction mixture was washed with water (2×200 mL). The organic layer was fractionally distilled to give (R)-styrene oxide (67.0 g, 64% yield, 99.3% ee).

Provenance & Evidence