Enantioselective ortho-Lithiation of Aminals of benzaldehyde chromiumtricarbonyl complex

✍ Scribed by Alexandre Alexakis; Tonis Kanger; Pierre Mangeney; Françoise Rose-Munch; Anne Perrotey; Eric Rose

• Book ID: 103976921
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 203 KB
• Volume: 6
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/0957-4166(94)00348-f

✦ Synopsis

The ayymmetric ortho lithiation of aminals of benzaldehyde chromiumtriearbonyl complex is described. The best regioisomeric composition is attained with aminal 2d. Quenching with an electrophile and hydrolysis of the aminal back to the aldehyde afford a single enantiomer of the o-substituted benzaldehyde chromiumtricarbonyl complex.

Chiral chromiumtricarbonyl arene complexes are useful synthons in asymmetric synthesis. 1 Their preparations lie usually in the resolution of diastereomeric derivatives 2 or enzymatic enantioselection. 3 We have recently demonstrated that enantioselective complexation of o-substituted chiral aminal derivatives of the corresponding aldehydes is a viable way to achieve this goal. 4

Recent interest in the selective o-metallation (versus o'-rnetallation) of arene chromiumtricarbonyl complexes led to highly diastereoselective preparation of o-substituted arene complexes. 5 The overall enantioselective process has been reported using either a chiral base as deprotonation reagent, 6 or a chiral acetal derivative of benzaldehyde or acetophenone chromiumtricarbonyl complex :7