aerobic asymmetric cyclization reaction of cinnamaldehydes and 1,3-dicarbonylcompounds through oxidative NHC-catalysis has been developed, and it allows the synthesis of a wide range of enantiomeric enriched dihydropyranone derivatives in good yields with good to excellent enantioselectivities. Various α,β-unsaturated aldehydes with aliphatic and aromatic substitution groups and 1,3-dicarbonyl compounds
Direct β-Activation of Saturated Aldehydes to Formal Michael Acceptors through Oxidative NHC Catalysis
作者:Junming Mo、Liang Shen、Yonggui Robin Chi
DOI:10.1002/anie.201302152
日期:2013.8.12
mediated by N‐heterocyclic carbenes (NHCs) enables the direct β‐carbon functionalization of saturated aldehydes (see scheme). The reaction proceeds through two sequential oxidative steps to generate α,β‐unsaturated triazolium ester equivalents as formal Michael acceptors, which react with 1,3‐diketones and β‐ketone esters in an enantioselective manner.
A straightforward N‐heterocycliccarbene (NHC)/LiCl‐mediated synthesis of dihydropyranones from α,β‐unsaturated carboxylic acids and 1,3‐dicarbonyl compounds was realized through the in situ activation strategy. The key advantages of this protocol include ready availability and high stability of starting materials, good yields, and excellent enantioselectivity.