N-Heterocyclic Carbene (NHC)-Catalyzed/Lewis Acid Mediated Conjugate Umpolung of Alkynyl Aldehydes for the Synthesis of Butenolides: A Formal [3+2] Annulation
作者:Jing Qi、Xingang Xie、Runfeng Han、Donghui Ma、Juan Yang、Xuegong She
DOI:10.1002/chem.201204386
日期:2013.3.25
Reverse to success! A new formal [3+2] annulation reaction combining alkynyl aldehydes and β,γ‐unsaturated α‐ketoesters has been disclosed by using a NHC‐catalyzed/Lewis acid mediated strategy. This cooperative catalysis strategy first allows the “allenolate” intermediate as a nucleophilic synthon at the β‐position to react with activated electrophilic reagents by an addition reaction as the key CC
Pd(<scp>ii</scp>)-catalyzed formal [4+1] cycloaddition reactions of diazoacetates and aryl propargyl alcohols to form 2,5-dihydrofurans
作者:Taoda Shi、Xin Guo、Shenghan Teng、Wenhao Hu
DOI:10.1039/c5cc05000f
日期:——
Pd(ii)-catalyzed auto-tandem formal [4+1] cycloaddition of diazoacetates and aryl propargyl alcohols affords 2,5-dihydrofurans as the dominant product over traditional ones.
A Cooperative N-Heterocyclic Carbene/Chiral Phosphate Catalysis System for Allenolate Annulations
作者:Anna Lee、Karl A. Scheidt
DOI:10.1002/anie.201403446
日期:2014.7.14
The highly enantioselective NHC‐catalyzed [3+2] annulation reaction with α,β‐alkynals and α‐ketoesters has been developed. A new mode of cooperativecatalysis involving the combination of a chiral Brønsted acid and a C1‐symmetric biaryl saturated‐imidazolium precatalyst was required to generate the desired γ‐crotonolactones in high yields and levels of enantioselectivity.
已开发出高对映选择性 NHC 催化的 [3+2] 与 α,β-炔醛和 α-酮酯的环化反应。需要一种新的协同催化模式,包括手性布朗斯台德酸和 C 1对称联芳基饱和咪唑鎓预催化剂的组合,以高产率和对映选择性水平生成所需的 γ-巴豆内酯。