Allene C(sp<sup>2</sup>)–H Activation and Alkenylation Catalyzed by Palladium
作者:Benedikt S. Schreib、Mina Son、Françoise A. Aouane、Mu-Hyun Baik、Erick M. Carreira
DOI:10.1021/jacs.1c11528
日期:2021.12.29
The selective transition-metal-mediated activation of C(sp2)–H bonds of allenes is a formidable challenge because of the competitive, intrinsic reactivity of cumulated double bonds. Herein, we report a Pd-catalyzed C–H alkenylation of electronically unbiased allenes, affording penta-1,2,4-triene products in up to 94% yield. A picolinamide directing group enables the formation of putative allenyl-palladacycles
Intramolecular Palladium(II)-Catalyzed 1,2-Addition to Allenes
作者:Catrin Jonasson、Attila Horváth、Jan-E. Bäckvall
DOI:10.1021/ja001748k
日期:2000.10.1
were performed in the presence of LiBr with Pd(OAc)2 as the catalyst. Two different reoxidants, p-benzoquinone or Cu(OAc)2, were used, the choice of oxidant being dependent on the substrate. The reaction proceeds through an external nucleophilic attack (Br-) on a (π-allene)palladium complex to produce a (π-allyl)palladium intermediate. Subsequent intramolecular attack by the second internal nucleophile
钯 (II) 催化分子内 1,2-加成到被内部亲核试剂取代的丙二烯。羧酸、醇、N-取代酰胺和氨基甲酸酯用作钯催化反应中的内部亲核试剂,以良好的分离产率提供内酯、四氢吡喃、四氢呋喃、吡咯烷和恶唑烷酮。该反应在 LiBr 存在下以 Pd(OAc)2 作为催化剂进行。使用了两种不同的再氧化剂,对苯醌或 Cu(OAc)2,氧化剂的选择取决于底物。该反应通过对(π-丙二烯)钯络合物的外部亲核攻击(Br-)进行,以产生(π-烯丙基)钯中间体。随后第二个内部亲核试剂的分子内攻击产生产物。中间体(π-烯丙基)钯配合物被分离和表征。研究了反应的范围和局限性及其机理和选择性,在不同的反应...
Gold(I)-Catalyzed Intramolecular Dihydroamination of Allenes with <i>N</i>,<i>N</i>′-Disubstituted Ureas To Form Bicyclic Imidazolidin-2-ones
作者:Hao Li、Ross A. Widenhoefer
DOI:10.1021/ol900730w
日期:2009.6.18
mixture of gold(I) N-heterocyclic carbene complex (5)AuCl [5 = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine] and AgPF6 at room temperature for 2 h led to isolation of bicyclic imidazolidin-2-one 4 in 93% yield with ≥98% diastereomeric purity. Gold-catalyzed dihydroamination was effective for a number of N-δ- and N-γ-allenyl ureas to form the corresponding bicyclic imidazolidin-2-ones in good yield
Photoinduced Chloroamination Cyclization Cascade with <i>N</i>-Chlorosuccinimide: From <i>N</i>-(Allenyl)sulfonylamides to 2-(1-Chlorovinyl)pyrrolidines
chloroamination cyclization of allenes bearing a tethered sulfonylamido group to afford 2-(1-chlorovinyl)pyrrolidines and related heterocycles in the presence of N-chlorosuccinimide (NCS) as the chlorine source. An in depth experimental and computational mechanistic study revealed the existence of multiple reaction pathways leading to a common nitrogen centered radical (NCR). This key NCR can be, in fact