One-pot synthesis of pyrrolidino- and piperidinoquinolinones by three-component aza-Diels–Alder reactions of in situ generated N-arylimines and cyclic enamides

Chiral dendrigraft polymer for asymmetric synthesis of isoquinuclidines

A copper complex of chiral modified dendrigraft amidoamine polymer with a pentaerythritol initiated polyepichlorohydrin core, PEN-G₂, on a solid resin support is employed in the synthesis of isoquinuclidines via aza Diels–Alder reaction between cyclohexenone and imines.

Modular, flexible, and stereoselective synthesis of pyrroloquinolines: rapid assembly of complex heterocyclic scaffolds

A novel 1,2-dinucleophile engages two imines in a sequential vinylogous Mannich-Mannich-Pictet-Spengler process to generate complex hexahydropyrrolo[3,2-c]quinolines in a one-pot operation. This methodology provides a rapid, highly modular, and flexible access toward a wide range of products and forms four new σ-bonds and chiral centers each. The diastereoselectivity may be inverted by fine-tuning of reaction conditions and the electronic nature of the imines.

Three-component aza-Diels-Alder reactions using Yb(OTf)3 catalyst under conventional/ultrasonic techniques

The Yb(OTf)3 catalyzed formal aza-Diels-Alder (or Povarov) reaction of cyclopentadiene and 1,3-cyclohexadiene with in situ-generated N-arylimines under conventional/ultrasonic techniques is herein described. This kind of three-component Povarov reaction results in quinoline and phenanthridine derivatives, which are important biological compounds.

Redox-neutral α-oxygenation of amines: reaction development and elucidation of the mechanism

Cyclic secondary amines and 2-hydroxybenzaldehydes or related ketones react to furnish benzo[e][1,3]oxazine structures in generally good yields. This overall redox-neutral amine α-C-H functionalization features a combined reductive N-alkylation/oxidative α-functionalization and is catalyzed by acetic acid. In contrast to previous reports, no external oxidants or metal catalysts are required. Reactions performed under modified conditions lead to an apparent reductive amination and the formation of o-hydroxybenzylamines in a process that involves the oxidation of a second equivalent of amine. A detailed computational study employing density functional theory compares different mechanistic pathways and is used to explain the observed experimental findings. Furthermore, these results also reveal the origin of the catalytic efficiency of acetic acid in these transformations.

Synthesis of highly functionalized pyrrolidines as tunable templates for the direct access to (±)-coerulescine and the tricyclic core of martinellines

An aza-Michael induced ring closure (aza-MIRC) tandem reaction of benzyl (2-bromoethyl)carbamate with various Michael acceptors is described. The N-Cbz-β-gem-disubstituted pyrrolidines thus obtained were proved to be versatile intermediates for the rapid access to both martinelline and spirooxindole backbones. An application of this strategy towards an expedient 4 step total synthesis of (±)-coerulescine is also presented.