Synthesis of 2- and 2,3-Substituted Pyrazolo[1,5-a]pyridines: Scope and Mechanistic Considerations of a Domino Direct Alkynylation and Cyclization of N-Iminopyridinium Ylides Using Alkenyl Bromides, Alkenyl Iodides, and Alkynes
摘要:
Direct functionalization and tandem processes have both received considerable recent interest due to their cost and time efficiency. Herein we report the synthesis of difficult to obtain 2-substituted pyrazolo[1,5-a]pyridines through a tandem palladium-catalyzed/silver-mediated elimination/direct functionalization/cyclization reaction involving N-benzoyliminopyridinium ylides. As such, these biologically important molecules are prepared in an efficient, high-yielding manner, only requiring a two-step sequence from pyridine. Aryl-substituted alkenyl bromides and iodides are effective ylide coupling partners. Mechanistic studies led to the use of terminal alkynes, which extended the scope of the reaction to include alkyl substitution on the unsaturated reactive site. The optimization, scope, and mechanistic considerations of the process are discussed.
A Cu-mediated preparation of 2-substitiuted pyrazolo[1,5-a]pyridines from N-benzoylpyridinium imides and terminal alkynes is described using stoichiometric Cu(OAc)2 as both the mediator and the oxidant. Extensive DFT calculations suggest a Cu(III) intermediate via disproportionation of Cu(II).
描述了使用化学计量的Cu(OAc)2作为介体和氧化剂,由N-苯甲酰基吡啶鎓酰亚胺和末端炔烃组成的Cu介导的2取代吡唑并[1,5- a ]吡啶的制备方法。广泛的DFT计算表明,通过Cu(II)歧化可以生成Cu(III)中间体。
Copper-catalyzed direct oxidative annulation of N-iminopyridinium ylides with terminal alkynes using O<sub>2</sub>as oxidant
作者:Shengtao Ding、Yuepeng Yan、Ning Jiao
DOI:10.1039/c2cc33706a
日期:——
The aerobic direct dehydrogenative annulation of N-iminopyridinium ylides with terminal alkynes leading to pyrazolo[1,5-a]pyridine derivatives has been developed.
Synthesis of 2-Substituted Pyrazolo[1,5-<i>a</i>]pyridines through Cascade Direct Alkenylation/Cyclization Reactions
作者:James J. Mousseau、Angélique Fortier、André B. Charette
DOI:10.1021/ol902710f
日期:2010.2.5
from N-iminopyridinium ylides is described. These medicinally interesting compounds are formed through a cascadeprocess involving a palladium-catalyzed direct alkenylation reaction followed by silver-mediated cyclization. The reaction can be performed with a wide range of electron-poor and electron-rich alkenyl iodides in good yields. This work represents perhaps the most direct route for the preparation
描述了由N-亚氨基吡啶鎓的叶立德合成2-取代的吡唑并[1,5- a ]吡啶。这些医学上有趣的化合物是通过级联过程形成的,该过程涉及钯催化的直接烯基化反应,然后进行银介导的环化反应。该反应可与多种贫电子和富电子的烯基碘化物以高收率进行。这项工作可能代表了制备这些化合物的最直接途径。
Base-mediated [3 + 2]-cycloannulation strategy for the synthesis of pyrazolo[1,5-<i>a</i>]pyridine derivatives using (<i>E</i>)-β-iodovinyl sulfones
with 1-aminopyridinium iodide is realized to access 2-substituted pyrazolo[1,5-a]pyridines in good to high yields. An essential modification of the dipolar N-tosylpyridinium imide allows the first preparative synthesis of 3-sulfonyl-pyrazolo[1,5-a]pyridines in moderate to high yields. Of note, the metal-free protocol features a broad substrate scope with good functional group tolerance and compatibility
吡唑并[1,5- a ]吡啶继续在药物化学中占据特殊地位,但3-磺酰基类似物的直接构建仍未探索。在碱性条件下,吡啶鎓-N-胺和相应的偶极胺在使用( E )-β-碘乙烯基砜的[3 + 2]-环加成反应中发挥了重要作用。K 2 CO 3介导的 ( E )-β-碘乙烯基砜与 1-氨基吡啶碘化物的串联环环脱磺酰基化反应以良好至高产率获得 2-取代的吡唑并[1,5- a ]吡啶。偶极N的基本修改-tosylpyridinium imide 首次以中等至高产率制备合成 3-磺酰基-吡唑并[1,5- a ] 吡啶。值得注意的是,无金属协议具有广泛的底物范围,具有良好的官能团耐受性和兼容性。通过克级反应证明了该过程的有效性,并根据具体结果提出了合理的机制。
Synthesis of 2- and 2,3-Substituted Pyrazolo[1,5-<i>a</i>]pyridines: Scope and Mechanistic Considerations of a Domino Direct Alkynylation and Cyclization of <i>N</i>-Iminopyridinium Ylides Using Alkenyl Bromides, Alkenyl Iodides, and Alkynes
作者:James J. Mousseau、James A. Bull、Carolyn L. Ladd、Angélique Fortier、Daniela Sustac Roman、André B. Charette
DOI:10.1021/jo201303x
日期:2011.10.21
Direct functionalization and tandem processes have both received considerable recent interest due to their cost and time efficiency. Herein we report the synthesis of difficult to obtain 2-substituted pyrazolo[1,5-a]pyridines through a tandem palladium-catalyzed/silver-mediated elimination/direct functionalization/cyclization reaction involving N-benzoyliminopyridinium ylides. As such, these biologically important molecules are prepared in an efficient, high-yielding manner, only requiring a two-step sequence from pyridine. Aryl-substituted alkenyl bromides and iodides are effective ylide coupling partners. Mechanistic studies led to the use of terminal alkynes, which extended the scope of the reaction to include alkyl substitution on the unsaturated reactive site. The optimization, scope, and mechanistic considerations of the process are discussed.