Effect of Bronsted Acids and Bases, and Lewis Acid (Sn<sup>2+</sup>) on the Regiochemistry of the Reaction of Amines with Trifluoromethyl-β-diketones: Reaction of 3-Aminopyrrole to Selectively Produce Regioisomeric 1<i>H</i>-Pyrrolo[3,2-<i>b</i>]pyridines
作者:Michael De Rosa、David Arnold、Douglas Hartline、Linda Truong、Roman Verner、Tianwei Wang、Christian Westin
DOI:10.1021/acs.joc.5b02192
日期:2015.12.18
Reaction of 3-aminopyrrole (as its salt) with trifluoromethyl-β-diketones gave γ-1H-pyrrolo[3,2-b]pyridines via reaction at the less reactive carbonyl group. The trifluoromethyl group increased the electrophilicity of the adjacent carbonyl group and decreased the basicity of the hydroxyl group of the CF3 amino alcohol formed. This amino alcohol was formed faster, but its subsequent dehydration to the
3-氨基吡咯(作为其盐)与三氟甲基-β-二酮反应,通过在反应性较低的羰基上反应,得到γ- 1H-吡咯并[3,2- b ]吡啶。三氟甲基增加了相邻羰基的亲电性,并降低了所形成的CF 3氨基醇羟基的碱性。该氨基醇形成较快,但随后脱水为β-烯胺酮的速度较慢,导致优先形成γ-区域异构体。使用一系列6种胺缓冲剂进行4,4,4-三氟-1-苯基-1,3-丁二酮与3-氨基吡咯的反应。α- 1H-吡咯并[3,2- b ]吡啶的产率随p K a的增加而增加胺缓冲液的浓度降低。出乎意料的是,产量以较高的p K a s下降。随着反应混合物变得更碱性,机理发生了变化。与强胺一起,三氟甲基-β-二酮主要或完全作为烯醇化物存在。在还原条件下(3-硝基吡咯/ Sn / AcOH /三氟甲基-β-二酮),α- 1H-吡咯并[3,2- b ]吡啶是由Sn 2+路易斯酸催化的主要产物。当3-氨基吡咯盐与三氟甲基-β-二酮的反应