A highly efficient [8 + 2] cycloaddition reaction of azaheptafulvenes with α-chloro aliphatic aldehydes enabled by N-heterocyclic carbene catalysis is presented, delivering cis-cycloheptatriene-fused γ-lactams with good yields, moderate to good diastereoselectivies, and excellent enantioselectivies. This higher order cycloaddition reaction can be readily expanded to the gram scale, and the products
Highly enantioselective [4 + 2] cyclization of chloroaldehydes and 1-azadienes catalyzed by N-heterocyclic carbenes
作者:Teng-Yue Jian、Li-Hui Sun、Song Ye
DOI:10.1039/c2cc35273g
日期:——
Highly functionalized dihydropyridinones were synthesized via the N-heterocyclic carbene-catalyzed enantioselective [4 + 2] annulation of alpha-chloroaldehydes and azadienes. Hydrogenation of the resulted dihydropyridinones afforded the corresponding piperidinones with high enantiopurity.
A novel carbonyl alkynylation has been accomplished based on utilization of the Meerwein-Ponndorf-Verley (MPV) reaction system. The success of the MPV alkynylation crucially depends on the discovery of the remarkable ligand acceleration effect of 2,2'-biphenol. For example, the alkynylation of chloral (2c) with the aluminium alkoxide 6(R = Ph), prepared in situ from Me(3)Al, 2,2'-biphenol and 2-me
Microwave-Assisted Synthesis of Heterocycles by Rhodium(III)-Catalyzed Annulation of <i>N</i>
-Methoxyamides with α-Chloroaldehydes
作者:Ji-Rong Huang、Carsten Bolm
DOI:10.1002/anie.201710776
日期:2017.12.11
α‐Chloroaldehydes have been used as alkyne equivalents in rhodium‐catalyzed syntheses of isoquinolones and 3,4‐dihydroisoquinolins starting from N‐methoxyamides. Compared to the existing technology, a complementary regioselectivity is achieved. Mechanistic investigations have been performed, and it was found that steric effects of both substrate and additive determine the product selectivity. Various
N-Heterocyclic Carbene-Promoted [4+2] Annulation of α-Chloro Hydrazones with α-Chloro Aliphatic Aldehydes to Access Enantioenriched Dihydropyridazinones
作者:Yipeng Zhou、Hongwei Zhou、Jianfeng Xu
DOI:10.1021/acs.joc.1c02581
日期:2022.3.4
α-chloro hydrazones and α-chloro aliphaticaldehydes via N-heterocycliccarbene (NHC) catalysis is outlined. These in situ-generated 1,2-diaza-1,3-dienes undergo asymmetric [4+2] annulation with NHC-bound enolates to afford the desired products bearing a stereogenic center at the C4 position. The notable features of this approach include good to excellent enantioselectivities, high functional group tolerance