Lewis-acid-induced reactions of α-methoxyglycinamide derivatives with silyl enol ethers. Formation of 3-amino-2-pyrrolidinones and 3-amino-2-pyrrolinones

✍ Scribed by Eric C. Roos; Henk Hiemstra; W. Nico Speckamp; Bernard Kaptein; Johan Kamphuis; Hans E. Schoemaker

• Book ID: 104589435
• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 554 KB
• Volume: 111
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19921110705

✦ Synopsis

Abstract

In order to develop an expedient synthetic route to γ‐oxo‐α‐aminocarboxamides, five different α‐(alkoxycarbonyl)amino‐α‐methoxyacetamides were subjected to borontrifluoride‐etherate‐mediated reactions with one silyl ketene acetal and four silyl enol ethers. Reactions of primary and secondary amides did not lead to the desired CCbond formation. Reactions of the tertiary N,N‐dimethylamide gave the expected γ‐oxo‐α‐aminocarboxamides. The reaction of an N‐methoxy‐N‐trimethylsilylcarboxamide with the ketene acetal also proceeded normally. However, the initial products of the latter amide with silyl enol ethers reacted further by cyclization, respectively, to give a cyclic N‐ methoxy‐N‐acyliminium intermediate. Depending on structural features of the enol ether used, this iminium intermediate suffered either proton loss and isomerization to give protected 3‐amino‐1‐methoxy‐δ^3^‐pyrrolin‐2‐ones, or underwent a second coupling with the enol ether to give protected 3‐amino‐1‐methoxypyrrolidin‐2‐ones.