Palladium-Catalyzed Regioselective Alkynylation of Pyrroles and Azoles under Mild Conditions: Application to the Synthesis of a Dopamine D-4 Receptor Agonist
摘要:
A mild and general method for the direct alkynylation of azoles such as pyrrole, indole, and 7-azaindole is described here. Using a simple catalytic system such as Pd(OAc)(2) (2.5 mol %), P(tBu)(2)Me center dot HBF4 (5 mol %), and NaOAc (2 equiv) allowed the regioselective introduction of various alkynyl residues at the C-2 position of pyrroles. Interestingly, C-2 alkynylation was also observed on C-3-substituted indoles, whereas classical C-3 alkynylation was obtained on selected unsubstituted indoles and 7-azaindole. Our methodology has been illustrated by the efficient synthesis of a potential schizophrenia drug (dopamine D-4 inhibitor).
Regiochemistry in Cobalt-Mediated Intermolecular Pauson–Khand Reactions of Unsymmetrical Internal Heteroaromatic Alkynes with Norbornene
作者:Benjamin E. Moulton、Adrian C. Whitwood、Anne K. Duhme-Klair、Jason M. Lynam、Ian J. S. Fairlamb
DOI:10.1021/jo200664m
日期:2011.7.1
comparable (2-phenylethynyl)heteroaromatic compounds with norbornene, mediated by Co2(CO)8 to give cyclopentenone products, were examined in this study. A synthetic protocol utilizing focused-microwave dielectric heating proved indispensable in the efficient synthesis of the PK cyclopentenone products. “π-Deficient” heteroaromatic substrates, e.g., 2-pyrones, and some “π-excessive” heteroaromatics such as
Co 2(CO)8介导的空间可比的(2-苯基乙炔基)杂芳族化合物与降冰片烯的分子间Pauson-Khand(PK)反应得到环戊烯酮产品,在这项研究中进行了检查。事实证明,利用聚焦微波介电加热的合成协议是有效合成PK环戊烯酮产品必不可少的。“π缺陷”杂芳族底物(例如2-吡喃酮)和一些“π过量”杂芳族化合物(例如2-和3-噻吩和2-呋喃)有利于新形成的环戊烯酮环中的β位置。其他π过量的杂芳族化合物(例如2-吡咯或2-吲哚)偏向α位。π-过量的3-吲哚衍生物给出了几乎相等的区域异构体混合物。氮在含吡啶基炔烃底物中的位置也影响PK反应的区域化学结果。拥有近端氮原子的2-吡啶基炔烃相对于4-吡啶基变异体会极大地影响区域选择性,有利于新形成的环戊烯酮环中的β位置。2-嘧啶炔基表现出与2-吡啶炔基相似的行为。不参与与降冰片烯进行PK反应的化合物包括(2-苯基乙炔基)咪唑和相关的苯并咪唑类,它们可促进原位生成的快速分解(μ2-炔)Co
Regio- and Stereoselective Chlorocyanation of Alkynes
作者:Alejandro G. Barrado、Adam Zieliński、Richard Goddard、Manuel Alcarazo
DOI:10.1002/anie.201705851
日期:2017.10.16
A variety of terminal and internal alkynes were converted regio‐ and stereoselectively into (Z)‐3‐chloroacrylonitriles by treatment with BCl3 in the presence of stoichiometric amounts of imidazolium thiocyanates. These products could be readily functionalized to provide useful building blocks, thus demonstrating the synthetic value of the method. Preliminary mechanistic studies suggest initial activation