Enantioselective construction of cis-hydroindole scaffolds via an asymmetric inverse-electron-demand Diels–Alder reaction: application to the formal total synthesis of (+)-minovincine

Abstract

cis-hydroindole scaffolds are widely existed in a large number of natural products, pharmaceutics, and organocatalysts. Therefore, the development of efficient and enantioselective methods for the construction of cis-hydroindoles is of...

Selective [2σ + 2σ] Cycloaddition Enabled by Boronyl Radical Catalysis: Synthesis of Highly Substituted Bicyclo[3.1.1]heptanes

“…Consequently, if possible, cycloaddition reactions are often the privileged options in synthetic design of ring molecules, particularly for carbocycles where heteroatoms as potential “biting points” are absent. For example, many elegant total syntheses of natural products have used the venerable Diels–Alder [4 + 2] cycloaddition as the key step for rapidly building six-membered rings or Pauson–Khand [2 + 2 + 1] cycloaddition for five-membered rings . In the reported cycloadditions over more than hundred years, apparently at least one π bond was required in the reactant molecule (Scheme A).…”

Diastereo‐ and Enantioselective Inverse‐Electron‐Demand Diels–Alder Cycloaddition between 2‐Pyrones and Acyclic Enol Ethers

“…A huge step forward was taken when the group of Cai reported the enantioselective IEDDA reaction of 2‐pyrone and cyclic dienophiles using a combination of Yb(OTf) 3 and a modified BINOL ligand. [ 6 , 7 ] However, the enantioselective IEDDA reaction of 2‐pyrones with acyclic 1,2‐disubstituted dienophiles remains elusive. Only one example was reported by Gademann and co‐workers, where an alkenyl selenide undergoes an IEDDA reaction with a 2‐pyrone derivative, affording the corresponding bridged bicyclic lactone with 84 % ee.…”

Asymmetric Catalytic Conjugate Addition of Cyanide to Chromones and β-Substituted Cyclohexenones

“…As shown in Scheme a, for the reaction of chromone 1a , the addition of pyridine was beneficial to the enantioselectivity. According to our previous studies, we speculated that pyridine could act as an auxiliary ligand to fill the widened pocket by the L 3 -PrMe 2 /Ce­(OTf) 3 complex catalyst, , lowering the coordination flexibility of the monodentate chromone substrate. The use of an excess amount of TMSCN resulted in the accompanying formation of the dicyanation byproduct 2a′ , indicating that the reaction is not initiated from 1,2-cyanation and retro-cyanation processes .…”

“…Motivated by fine-tuned chiral N,N ′-dioxide/metal complex catalysts with wide compatibility of various metal ions and our previous studies on the asymmetric addition reactions of cyanide and others, we rationalize that these catalysts are suitable for enantioselective 1,4-cyanation of cyclic enones. Herein, we wish to disclose our research along this line.…”