Radical Enamination of Vinyl Azides: Direct Synthesis of N-Unprotected Enamines
摘要:
An electron-withdrawing-group-generable radical-induced enamination of vinyl azides is reported, which results in a variety of beta-functionalized N-unprotected enamines in a stereoselective manner. A plausible mechanism involving an unusual 1,3-H transfer of in situ generated iminyl radical intermediate was proposed on the basis of experimental results and DFT calculations.
The Iridium-catalyzed enantioselective couplingreaction of vinyl azides and allylic electrophiles is presented and provides access to β-chiral carbonyl derivatives. Vinyl azide are used as acetamide enolate or acetonitrile carbanion surrogates, leading to γ,δ-unsaturated β-substituted amides as well as nitriles with excellent enantiomeric excess. The products are readily transformed into chiral N-containing
AgN<sub>3</sub>-Catalyzed Hydroazidation of Terminal Alkynes and Mechanistic Studies
作者:Shanshan Cao、Qinghe Ji、Huaizhi Li、Maolin Pang、Haiyan Yuan、Jingping Zhang、Xihe Bi
DOI:10.1021/jacs.0c00836
日期:2020.4.15
hydroazidation of alkynes is the most straightforward way to access vinyl azides - versatile building blocks in organic synthesis. We previously realized such a fundamental reaction of terminalalkynes using Ag2CO3 as a catalyst. However, the high catalyst loading seriously limits its practicality, and moreover the exact reaction mechanism remains unclear. Here, on the basis of X-ray diffraction studies on the
The direct addition of in situgenerated hydrazoic acid to alkynes is realized without solvent by using a gold catalyst derived from a recently designed remotely functionalized biaryl-2-ylphosphine ligand (i.e., WangPhos). With terminal alkynes, the additions are mostly realized with 0.1 mol% catalyst loadings and at 40 °C. With more challenging internal alkynes devoid of direct EWG substitution, the
Synthesis of β-Difluoroalkyl Azides via Elusive 1,2-Azide Migration
作者:Yongquan Ning、Paramasivam Sivaguru、Giuseppe Zanoni、Edward A. Anderson、Xihe Bi
DOI:10.1016/j.chempr.2019.12.004
日期:2020.2
development of azide migration reactions is a formidable challenge because of the potential competition of side processes driven by the release of molecular nitrogen. Here, we report a conceptually novel 1,2-azide migration in an unprecedented gem-difluorination of the readily available α-vinyl azides, a transformation that enables the synthesis of a range of novel β-difluorinated alkyl azides. The practicality
Vinyl Azides as Radical Acceptors in the Vitamin B<sub>12</sub>-Catalyzed Synthesis of Unsymmetrical Ketones
作者:Krzysztof R. Dworakowski、Sabina Pisarek、Sidra Hassan、Dorota Gryko
DOI:10.1021/acs.orglett.1c03321
日期:2021.12.3
Vinyl azides are very reactive species and as such are useful building blocks, in particular, in the synthesis of N-heterocycles. They can also serve as precursors of ketones. These form in reactions of vinyl azides with nucleophiles or radicals. We have found, however, that under light irradiation vitamin B12 catalyzes the reaction of vinyl azides with electrophiles to afford unsymmetrical carbonyl
乙烯基叠氮化物是非常活泼的物质,因此是有用的结构单元,特别是在N-杂环的合成中。它们还可以作为酮的前体。这些是在乙烯基叠氮化物与亲核试剂或自由基的反应中形成的。然而,我们发现,在光照射下,维生素 B 12催化乙烯基叠氮化物与亲电子试剂的反应,以良好的产率提供不对称羰基化合物。机理研究表明烷基自由基是这种转变的关键中间体。