Abstract: Treatment of a 1: l: l mixture of enolate 5: amine 6: lithium amide 7 with BF3. OEt2 affords the naproxen amide 4a with an enantiomer excess of 77%(> 90% yield). The result is attributed to Lewis acid-induced internal proton return (ipr) in a mixed aggregate containing the enolate and the chiral amine. Use of proline-derived diamines 9 and 10 in place of 6 affords 4a with 56-66% ee, but monoamines are relatively ineffective. Similar ipr ...
