Reactions of enols of amides with diazomethane
Reactions of enols of amides with diazomethane
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DOI：
10.1021/jo0203802
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发表时间：
2002-10-04
影响因子：
3.6
通讯作者：
Rappoport, Z
中科院分区：
文献类型：
--
作者：
Lei, YX;Rappoport, Z
研究了由两个完全或部分以烯醇形式存在的-吸电子基团激活的10种羧胺与重氮甲烷的反应。主要结果是观察到的反应的多样性。酸性最强的烯醇3-7，被至少一个三氟乙氧羰基或氰基激活，发生O-甲基化或O， n -二甲基化。在β -二甲氧基羰基活化体系5和8中，酰胺形式的c -甲基化产物是产物之一。Meldrum's酸苯胺烯醇2发生裂解，导致c -烷基化亚胺具有CH(CO2Me)(2)基团。在Me2CHNHC(OH) = C(CO2CH2CF3)(2) 4的C， n -二甲基化产物中，一个2,2,2-三氟乙氧羰基被一个甲氧羰基交换。2-苯胺-1,3-环戊二酮10在一个环羰基上甲基化，而1,3-吲哚二酮类似物11的烯醇与三个重氮甲烷分子反应，发生环扩张和o-甲基化，生成3-苯胺-1,4-二甲氧基萘。结果表明，该反应是由烯醇对重氮甲烷的质子化引起的，烯醇和k -烯醇的酸度与反应的区域选择性之间存在近似的定性关系。
The reaction of 10 carboxamides activated by two beta-electron-withdrawing groups, which mostly exist completely or partially in their enol forms, with diazomethane was investigated. The main outcome is the diversity of reactions observed. With the most acidic enols 3-7, activated by at least one trifluoroethoxycarbonyl group or a cyano group, O-methylation or O,N-dimethylation takes place. With beta-dimethoxycarbonyl-activated systems 5 and 8, the C-methylation product of the amide form was one of the products. With a Meldrum's acid anilide enol 2, a cleavage took place leading to the C-alkylated imine having a CH(CO2Me)(2) group. Exchange of one 2,2,2-trifluoroethoxycarbonyl by a methoxycarbonyl in the C,N-dimethylation product of Me2CHNHC(OH) = C(CO2CH2CF3)(2) 4 took place. The 2-anilido-1,3-cyclopentanedione 10 was methylated on a ring carbonyl while the enol of the 1,3-indanedione analogue 11 reacted with three diazomethane molecules and underwent a ring expansion and O-methylation to the 3-anilido-1,4-dimethoxynaphthalene. It is suggested that the reaction initiates by protonation of the diazomethane by the enol and an approximate qualitative relationship exists between the acidity of the enol and K-enol and the regioselectivity of the reaction.