Triflic anhydride mediated cyclization of 5-hydroxy-substituted pyrrolidinones for the preparation of alpha-trifluoromethylsulfonamido furans.
Triflic anhydride mediated cyclization of 5-hydroxy-substituted pyrrolidinones for the preparation of alpha-trifluoromethylsulfonamido furans.
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DOI：
10.1021/jo0341970
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发表时间：
2003-06
期刊：
影响因子：
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通讯作者：
A. Padwa;P. Rashatasakhon;M. Rose
中科院分区：
文献类型：
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作者：
A. Padwa;P. Rashatasakhon;M. Rose
α-当归内酯与烷基胺在水相条件下反应，高产率地得到5-羟基-5-甲基吡咯烷酮。当反应在无水条件下进行时，获得的唯一产物是相应的4-氧代戊酸酰胺。在吡啶中用三氟甲磺酸酐（Tf（2）O）处理这两类化合物，导致形成各种取代的磺酰胺基呋喃。建议的机制涉及初始形成的亚胺离子，随后转化为瞬态亚氨基三氟甲磺酸酯。高度亲电亚胺在相邻羰基的氧原子上的环化产生亚氨基二氢呋喃中间体。该物质进一步与另一当量的Tf（2）O反应，得到观察到的产物。发现所用刘易斯酸的性质影响环化反应的结果。在某些情况下，磺酰胺呋喃被用作合成吲哚啉和相关杂环系统的环加成底物。
The reaction of alpha-angelica lactone with alkylamines under aqueous conditions afforded 5-hydroxy-5-methylpyrrolidinones in high yield. When the reaction was carried out under anhydrous conditions, the only products obtained were the corresponding 4-oxopentanoic acid amides. Treatment of either class of compound with triflic anhydride (Tf(2)O) in pyridine resulted in the formation of various substituted sulfonamidofurans. The suggested mechanism involves initial formation of an iminium ion which is subsequently transformed into a transient imino triflate. Cyclization of the highly electrophilic imine onto the oxygen atom of the adjacent carbonyl group generates an imino dihydrofuran intermediate. This species reacts further with another equivalent of Tf(2)O to give the observed product. The nature of the Lewis acid used was found to affect the outcome of the cyclization reaction. In certain cases, the sulfonamide furan was utilized as a cycloaddition substrate for the synthesis of indolines and related heterocyclic systems.