Studies Dealing with Thionium Ion Promoted Mannich Cyclization Reactions
作者:Albert Padwa、Alex G. Waterson
DOI:10.1021/jo991414h
日期:2000.1.1
six-membered alkylthio-substituted lactams as transient intermediates. Further reaction of the alkylthio-substituted lactam with DMTSF generates an N-acyliminium ion, which undergoes cyclization with the tethered aromatic ring to produce an azapolycyclic ring system. Related cyclization sequences occur when amido thioacetals possessing simple olefinic tethers were used. The overall procedure represents an efficient
Diastereoselective Cycloadditions and Transformations of<i>N</i>-Alkyl and<i>N</i>-Aryl Maleimides with Chiral 9-Anthrylethanol Derivatives
作者:Harry Adams、Tareg M. Elsunaki、Isaac Ojea-Jiménez、Simon Jones、Anthony J. H. M. Meijer
DOI:10.1021/jo101437b
日期:2010.9.17
Thermal Diels-Alder reactions of chiral 9-methoxyethyl and 9-hydroxyethyl anthracene have been investigated both experimentally and computationally with a range of N-substituted maleimides. Whereas cycloadditions with 9-methoxyethyl anthracene proceeded with almost complete diastereselectivity, those with 1-anthracenc-9-yl-ethanol resulted in essentially no diastereoselectivity. Subsequent regio- and stereoselective transformations with reducing agents and carbon nucleophiles demonstrated the synthetic utility of this methodology, which was applied to the enantioselective synthesis of pyrrolo[2,1-a]isoquinolines and an attempted synthesis of the alkaloid crispine A. Computational studies supported the proposed hypotheses for the stereoselectivity observed in the transformations described.
Metalation <i>vs </i>Nucleophilic Addition in the Reactions of <i>N</i>-Phenethylimides with Organolithium Reagents. Ready Access to Isoquinoline Derivatives <i>via</i> <i>N</i>-Acyliminium Ions and Parham-Type Cyclizations
作者:M. Isabel Collado、Izaskun Manteca、Nuria Sotomayor、María-Jesús Villa、Esther Lete
DOI:10.1021/jo962155o
日期:1997.4.1
Sequential carbophilic addition of organolithium reagents and N-acyliminiumioncyclization of N-phenethylimides 1 affords the substituted isoquinolones 3 in high yields, with the possibility of varying the substituent at the C-1 position of the isoquinoline ring by changing the organolithium reagent. Ready access to the isoquinolinenucleus via Parham-typecyclization of imides 2 is also described
Concise total syntheses of berberine and its analogues enabled by trifluoroacetic anhydride-promoted decarbonylative-elimination reaction
作者:Xifei Yan、Jianfeng Zheng、Wei-Dong Z. Li
DOI:10.1016/j.tetlet.2023.154826
日期:2023.11
The total syntheses of berberine hydrochloride and itsanalogues were achieved by a convergent strategy from available meconine derivatives, which were based on base mediated isoquinoline annulation followed by trifluoroacetic anhydride promoted decarbonylative elimination protocol. Key elements of our approach feature divergent synthesis, step-economy manner, multigram scalable synthesis, transition