Pd-Catalyzed Bis-cyclization/Dimerization Reactions of ω-Aminovinyl Halides
摘要:
Palladium is shown to catalyze the dimerization and cyclization of vinyl halides to generate pyrrolidine and piperidine dimers connected by a trans-ethylene bridge. The reaction tolerates a variety of N-alkyl substituents, including adamantyl. This remarkable dimerization reaction generates the skeleton of the alkaloid hyalbidone in a single step. A crossover experiment with a vinyl halide and a vinyl bromide is consistent with a Michael-type addition to a vinylpalladium cation to generate a Pd(0) alkylidene intermediate.
A Pd-catalyzed reaction of vinyl iodides and N-tosylhydrazones that assembles eta(3)-allyl ligands through carbene insertion is demonstrated. Intramolecular trapping with nitrogen nucleophiles generates good yields of cinnamyl and pentadienyl amines like those found in alkaloid natural products. Carbenylative amination was the key reaction to complete the synthesis of the alkaloid caulophyllumine B. Migratory insertion was biased to provide allylamines with optical purity up to 64% ee, but in a lower yield.
Carbenylative Amination and Alkylation of Vinyl Iodides via Palladium Alkylidene Intermediates
作者:Ilandari Dewage Udara Anulal Premachandra、Thi A. Nguyen、Chengtian Shen、Eugene S. Gutman、David L. Van Vranken
DOI:10.1021/acs.orglett.5b02820
日期:2015.11.6
palladium-catalyzed reactions involving insertion of alkylidenes with α-hydrogens undergo β-hydride elimination from alkylpalladium(II) intermediates to form alkenes. Vinyl iodides were shown to generate η3-allylpalladium intermediates that resist β-hydride elimination, preserving the sp3 center adjacent to the carbene moiety. Acyclic stereocontrol (syn/anti) for carbenylative amination and alkylation reactions was
Palladium-Catalyzed Catellani Aminocyclopropanation Reactions with Vinyl Halides
作者:Avinash Khanna、Ilandari Dewage Udara Anulal Premachandra、Paul D. Sung、David L. Van Vranken
DOI:10.1021/ol401383m
日期:2013.6.21
intramolecular aminocyclopropanation of norbornenes with aliphatic vinylhalides in good yields. The reaction tolerates a variety of amine substituents and gives good results with a variety of carbocyclic and oxabicyclic [2.2.1] alkene acceptors. Notably, stabilized enolate nucleophiles were also employed in cyclopropanation reactions.
Palladium/GF-Phos-catalyzed asymmetric carbenylative amination to access chiral pyrrolidines and piperidines
作者:Yue Sun、Chun Ma、Zhiming Li、Junliang Zhang
DOI:10.1039/d2sc03999k
日期:——
but the development of catalyticenantioselective versions still poses considerable challenges and only very limited examples have been reported. We herein report an asymmetric palladium/GF-Phos-catalyzed carbenylative amination reaction of N-tosylhydrazones and (E)-vinyl iodides pendent with amine, which allows facile access to a range of chiral pyrrolidines and piperidines in good yields (45–93%)
N-甲苯磺酰腙的交叉偶联已成为构建结构多样化分子的有效方法,但催化对映选择性版本的开发仍然面临相当大的挑战,并且仅报道了非常有限的例子。我们在此报告了一种不对称钯/GF-Phos催化的N-甲苯磺酰腙和( E )-乙烯基碘化物与胺悬垂的羧基胺化反应,该反应可以轻松获得一系列手性吡咯烷和哌啶,产率良好(45-93%) ) 高达 96.5: 3.5 er 。此外,条件温和、底物范围广泛、制备规模化以及天然产物(−)-norruspoline的高效合成是该方法的实用特点。