Tandem Approach to Benzothieno- and Benzofuropyridines from o-Alkynyl Aldehydes via Silver-Catalyzed 6-endo-dig Ring Closure
摘要:
An operationally simple silver-catalyzed tandem strategy for the synthesis of benzothienopyridines 7a-t and benzofuropyridines 8a-p by the reaction of o-alkynyl aldehyde 4a-t and 5a-p with tert-butylamine 6 under mild reaction conditions is described. The present methodology provides a facile conversion of easily accessible o-alkynyl aldehydes into medicinally useful heterocycles in good to excellent yields under mild and environmentally friendly reaction conditions with excellent regioselectivity. The developed chemistry has been successfully extended for the selective synthesis of C-4 deuterated benzothienopyridines 7u-v and benzofurop-yridines 8q-r. The role of the ethanolic proton in the reaction was validated by deuterium-labeling experiments.
一种环境友好且操作简单的一锅法,用于在水中使用 AgI 作为催化剂从邻炔醛和芳胺中区域选择性串联合成多种取代的稠合苯并咪唑并 [2,1-a] 异喹啉、萘啶、噻吩并吡啶和喹喔啉被描述。该反应显示在更具亲电性的炔基碳上形成了选择性的 N-C 键,从而产生了区域选择性的 6-endo-dig 环化产物,产率很好。所提出的合成稠合杂环的机理途径是在环 B 之前形成环 A,环 B 是通过氮对炔基碳的第二次分子内攻击形成的,得到了分离的中间体 U 和环化产物 5a 的机械实验和 X 射线晶体学研究的支持。对比实验表明,分子内亲核攻击的可行性高于外部亲核试剂的分子间攻击。这种催化的绿色方案已有效地应用于水中的双串联环化。
Ag<sup>I</sup>-Catalyzed Cascade Strategy: Regioselective Access to Diversely Substituted Fused Benzimidazo[2,1-<i>a</i>]isoquinolines, Naphthyridines, Thienopyridines, and Quinoxalines in Water
bond formation on the more electrophilic alkynyl carbon, resulting in the regioselective 6-endo-dig cyclized products in good to excellent yields. The proposed mechanistic pathway for the synthesis of fused heterocycles proceedingthrough formation of ring A prior to ring B, which formed through a second intramolecular attack of the nitrogen onto the alkynyl carbon, was supported by mechanistic experiments
一种环境友好且操作简单的一锅法,用于在水中使用 AgI 作为催化剂从邻炔醛和芳胺中区域选择性串联合成多种取代的稠合苯并咪唑并 [2,1-a] 异喹啉、萘啶、噻吩并吡啶和喹喔啉被描述。该反应显示在更具亲电性的炔基碳上形成了选择性的 N-C 键,从而产生了区域选择性的 6-endo-dig 环化产物,产率很好。所提出的合成稠合杂环的机理途径是在环 B 之前形成环 A,环 B 是通过氮对炔基碳的第二次分子内攻击形成的,得到了分离的中间体 U 和环化产物 5a 的机械实验和 X 射线晶体学研究的支持。对比实验表明,分子内亲核攻击的可行性高于外部亲核试剂的分子间攻击。这种催化的绿色方案已有效地应用于水中的双串联环化。
Tandem Approach to Benzothieno- and Benzofuropyridines from <i>o</i>-Alkynyl Aldehydes via Silver-Catalyzed 6-<i>endo-dig</i> Ring Closure
作者:Sonu Kumar、Carlos Cruz-Hernández、Shilpi Pal、Rakesh K. Saunthwal、Monika Patel、Rakesh K. Tiwari、Eusebio Juaristi、Akhilesh K. Verma
DOI:10.1021/acs.joc.5b01647
日期:2015.11.6
An operationally simple silver-catalyzed tandem strategy for the synthesis of benzothienopyridines 7a-t and benzofuropyridines 8a-p by the reaction of o-alkynyl aldehyde 4a-t and 5a-p with tert-butylamine 6 under mild reaction conditions is described. The present methodology provides a facile conversion of easily accessible o-alkynyl aldehydes into medicinally useful heterocycles in good to excellent yields under mild and environmentally friendly reaction conditions with excellent regioselectivity. The developed chemistry has been successfully extended for the selective synthesis of C-4 deuterated benzothienopyridines 7u-v and benzofurop-yridines 8q-r. The role of the ethanolic proton in the reaction was validated by deuterium-labeling experiments.