Divergent selectivity in MgI2-mediated ring expansions of methylenecyclopropyl amides and imides
Divergent selectivity in MgI2-mediated ring expansions of methylenecyclopropyl amides and imides
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DOI：
10.1021/ja011110o
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发表时间：
2002-06-05
影响因子：
15
通讯作者：
Han, WS
中科院分区：
文献类型：
--
作者：
Lautens, M;Han, WS
我们报告了一种在 MgI2 存在下通过单活化亚甲基环丙烷 (MCP) 与醛亚胺和醛进行扩环来制备五元和六元杂环化合物的新方法。单活化的MCP充当同迈克尔受体以在MgI 2 存在下提供双功能插烯烯醇化物。单活化 MCP 的羰基部分极大地影响二烯醇化物中与芳基醛亚胺和醛的反应位点以及环的大小。观察到对五元杂环与六元杂环的优异发散选择性：α-烷基化/5-exo-tet 环化（Z = NPh2）VS、γ-烷基化/6-exo-trig 环化（Z = 2-恶唑烷酮）。类似地，MCP酰亚胺与烷基醛胺的反应通过改变亲电子试剂的尺寸或反应温度表现出相同的选择性。此外，我们观察到插烯酰亚胺烯醇化物与羰基化合物反应中形成γ-烷基化加合物的第一个例子。
We report a novel approach to prepare five- and six-membered heterocyclic compounds via a ring expansion of monoactivated methylenecyclopropanes (MCPs) with aldimines and aldehydes in the presence of MgI2. Monoactivated MCPs behave as homo-Michael acceptors to afford bifunctional vinylogous enolates in the presence Of MgI2. The carbonyl moiety of the monoactivated MCP dramatically influences the reaction site in the dienolate with aryl aldimines and aldehydes as well as the size of the ring. Excellent divergent selectivity to five- vs. six-membered heterocycles is observed: alpha-alkylation/5-exo-tet cyclization (Z = NPh2) VS, gamma-alkylation/6-exo-trig cyclization (Z = 2-oxazolidone). Analogously, the reaction of the MCP imide with alkyl aldmines demonstrates the same selectivity by varing the size of electrophile or the reaction temperature. In addition, we observe the first example of the formation of the gamma-alkylation adduct in the reaction of a vinylogous imide enolate with a carbonyl compound.