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
metal-free access to 3,6-disubstituted α-pyrones from α-chloro aldehydes and β-tosyl enones is reported. The reactions proceed via the Michael addition/lactonization/elimination cascade. The regioselective addition of NHC-bound enolates/homoenolates to the enones bearing a bulkier functionality such as tosyl group at the β-position has remained challenging. The 3,6-disubstituted α-pyrones could be converted
A facile N-heterocyclic carbene catalytic enantioselective aza-Diels–Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental
A tandem dearomatization/rearomatization strategy: enantioselective N-heterocyclic carbene-catalyzed α-arylation
作者:Zijun Wu、Jian Wang
DOI:10.1039/c8sc04601h
日期:——
the carbene-catalyzed tandem dearomatization/rearomatization reaction of azonaphthalenes with α-chloroaldehydes is described. This protocol enables the efficient assembly of chiral dihydrocinnolinone derivatives in good yields with excellent enantioselectivities (up to 99% ee). Moreover, this strategy enables not only the highlyenantioselective NHC-catalyzed nucleophilic aromatic substitution, but also
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