Triflic Anhydride Mediated Cyclization of 5-Hydroxy-Substituted Pyrrolidinones for the Preparation of α-Trifluoromethylsulfonamido Furans
作者:Albert Padwa、Paitoon Rashatasakhon、Mickea Rose
DOI:10.1021/jo0341970
日期:2003.6.1
(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
α-当归内酯与烷基胺在水性条件下的反应以高收率得到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-氧戊酸酰胺。用三氟甲磺酸酐(Tf(2)O)在吡啶中处理任一类化合物均导致形成各种取代的磺酰胺基呋喃。所建议的机理涉及亚胺离子的最初形成,其随后被转化为瞬态亚氨基三氟甲磺酸酯。将高度亲电的亚胺环化到相邻羰基的氧原子上,生成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。发现所使用的路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二氢吲哚和相关杂环系统的环加成底物。