A facile and efficient synthetic route to multi-substituted 2-aminopyridines has been developed via a formal [5C + 1N] annulation of readily available 2,4-pentadienenitriles with hydroxylamine (NH2OH) under very mild conditions, which involves sequential intermolecular aza-nucleophilic addition of hydroxylamine, intramolecular aza-cyclization, and dehydration reactions.
A strategy for the N-heterocycliccarbene (NHC) catalyzed asymmetric synthesis of 3,5-diaryl substituted cyclohexenones has been developed via oxidative [4+2] annulation of enals and alkenylisoxazoles. It is the first example of using NHC organocatalysis in a double vinylogous Michael type reaction, a challenging but highly desirable topic. This unprecedented protocol affords good yields as well as
Facile access to highly functionalized hydroisoquinoline derivatives<i>via</i>phosphine-catalyzed sequential [3+3]/[3+3] annulation
作者:Ning Li、Penghao Jia、You Huang
DOI:10.1039/c9cc05832j
日期:——
An unprecedented sequential [3+3]/[3+3] annulation of allenoates and dienes catalyzed by phosphine has been developed, which provides novel and facile access to highly functionalized hydroisoquinoline derivatives. The reaction features a wide reaction scope and mild reaction conditions. δ-sulfonamido-allenoates, acting as a five-atom unit, represent a new synthon in the reactions of allenoates.
Phosphine-Catalyzed Annulations between Modified Allylic Derivatives and Polar Dienes and Substituent Effect on the Annulation Mode
作者:Junjun Tian、Haiyun Sun、Rong Zhou、Zhengjie He
DOI:10.1002/cjoc.201300646
日期:2013.10
In this work, the phosphine‐catalyzed annulationreactions between modifiedallylic derivatives and polar 1,1‐dicyano‐1,3‐dienes have been studied. In the catalysis of PPh3 (20 mol%), a [4+1] annulationreaction is realized between a series of 1,1‐dicyano‐2,4‐diaryl‐1,3‐dienes and ethoxycarbonyl‐activatedallylic acetate, producing polysubstituted cyclopentenes in modest to excellent yields. It is
Unusual Formal [1+4] Annulation through Tandem P(NMe<sub>2</sub>
)<sub>3</sub>
-Mediated Cyclopropanation/Base-Catalyzed Cyclopropane Rearrangement: Facile Syntheses of Cyclopentenimines and Cyclopentenones
作者:Rong Zhou、Kai Zhang、Ling Han、Yusong Chen、Ruifeng Li、Zhengjie He
DOI:10.1002/chem.201505047
日期:2016.4.18
An unusual formal [1+4] annulation of α‐dicarbonyl compounds with 1,1‐dicyano‐1,3‐dienes has been realized, leading to facile syntheses of cyclopentenimines and cyclopentenones in a unique manner. Mechanistic investigation implies that this reaction takes place through a P(NMe2)3‐mediated cyclopropanation followed by a base‐catalyzed cyclopropane rearrangement. It therefore represents an unprecedented