Novel and stereoselective methods for the preparation of aromatic lactams via reductive coupling reactions mediated by SmI2

✍ Scribed by Hidemi Yoda; Keigo Matsuda; Hiroaki Nomura; Kunihiko Takabe

• Publisher: Elsevier Science
• Year: 2000
• Tongue: French
• Weight: 217 KB
• Volume: 41
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)00014-9

✦ Synopsis

Samarium(II) diiodide-mediated reductive cross-coupling of N-alkylated phthalimides with carbonyl compounds is shown to afford hydroxylated α-hydroxylactams. Ketoamides obtained by dehydration of these compounds through keto-enol tautomer isomerization were reduced with NaBH 4 in a completely stereoselective manner in the presence of CeCl 3 to give threo-aromatic lactams as the sole product. Direct reductive deoxygenation of these α-hydroxylactam intermediates with Et 3 SiH in the presence of Lewis acid also displayed high stereoselectivity to afford the same threo-lactams exclusively. The mechanistic origins of this stereoselectivity are briefly documented.