The highly stereoselective intermolecular all-carbon [4+2] annulation between in situ generated acyclic dienolates and α,β-unsaturatedacylazoliums is disclosed. The identification of 2-acyloxy-3-butenones as suitable diene precursors is the key to the success of this transformation. The corresponding highly functionalized cyclohexene products, which are inaccessible from Diels–Alder reactions, were
A Highly Enantioselective Chiral Lewis Base-Catalyzed Asymmetric Cyanation of Ketones
作者:Shi-Kai Tian、Li Deng
DOI:10.1021/ja010690m
日期:2001.6.1
A conceptually direct and attractive approach is to transform prochiral ketones to chiralbuildingblocks containing a quaternary stereocenter by a catalytic asymmetric C bond formation. The realization of this approach, however, has proven to be a formidable task. 1,2d,3 Achieving synthetically useful enantioselectivity with unconjugated aliphatic ketones is particularly challenging since the two
Copper-Catalyzed Successive C−C bond formations on Indoles or Pyrrole: A Convergent Synthesis of Symmetric and Unsymmetric Hydroxyl Substituted <i>N</i>
-H Carbazoles
C−Cbond formations on indoles and pyrrole approach for the direct synthesis of hydroxyl substitutedN‐H carbazoles is described. The current process represents an atom‐economical method for the preparation of both symmetric and unsymmetric densely substituted and hydroxyl containingN‐H carbazoles from easily accessible starting materials without the need for expensive metals and harsh reaction conditions
The umpolung of β,γ-unsaturated diketones through N-heterocyclic carbene catalysis is described, which allows access to a variety of highly functionalized bicyclic cyclohexene-β-lactones and 1,3,4-triaryl benzenes. An unprecedented reaction pattern involving the catalytic formation of nucleophilic O-acylated homoenolate intermediate is proposed. A diverse set of transformations on the product further