An enantioselective organocatalyzed aza-MBH domino process: application to the facile synthesis of tetrahydropyridines

Cu(I)-Induced Activation of Furan for Inverse Electron Demand ADAR with Alkenes toward Regioselective Synthesis of Tetrahydropyridine

The aza-Diels-Alder reaction of various alkenes and in situ formed 1-aza-1,3-dienes from the reaction of furan/pyrrole/thiophene and PhINTs for the regioselective synthesis of tetrahydropyridine (THP) derivatives was realized. The reaction was catalyzed by Tp^Me2Cu as a catalyst under very mild reaction conditions. Structurally different alkenes, along with an alkyne, have been utilized as dienophiles to afford a wide range of different THP derivatives up to 70% yield. The potential application of the envisaged method was also investigated by a gram-scale synthesis.

Organocatalytic Synthesis of Highly Functionalized Heterocycles by Enantioselective aza-Morita-Baylis-Hillman-Type Domino Reactions

Organocatalytic enantioselective domino reactions are an extremely attractive methodology, as their use enables the construction of complex chiral skeletons from readily available starting materials in two or more steps by a single operation under mild reaction conditions. Thus, these reactions can save both the quantity of chemicals and length of time typically required for the isolation and/or purification of synthetic intermediates. Additionally, no metal contamination of the products occurs, given that organocatalysts include no expensive or toxic metals. The aza-Morita-Baylis-Hillman (aza-MBH) reaction is an atom-economical carbon-carbon bond-forming reaction between α,β-unsaturated carbonyl compounds and imines mediated by Lewis base (LB) catalysts, such as nucleophilic phosphines and amines. aza-MBH products are functionalized chiral β-amino acid derivatives that are highly valuable as pharmaceutical raw materials. Although various enantioselective aza-MBH processes have been investigated, very few studies of aza-MBH-type domino reactions have been reported due to the complexity of the aza-MBH process, which involves a Michael/Mannich/H-transfer/β-elimination sequence. Accordingly, in this review article, our recent efforts in the development of enantioselective domino reactions initiated by MBH processes are described. In the domino reactions, chiral organocatalysts bearing Brønsted acid (BA) and/or LB units impart synergistic activation to substrates, leading to the easy synthesis of highly functionalized heterocycles (some of which have tetrasubstituted and/or quaternary carbon stereocenters) in high yield and enantioselectivity.

A stereoselective sequential organocascade and multicomponent approach for the preparation of tetrahydropyridines and chimeric derivatives

A stereoselective multicomponent approach leading to a novel class of pentasubstituted tetrahydropyridines is described.

An enantioselective organocatalyzed aza-Morita-Baylis-Hillman reaction of isatin-derived ketimines with acrolein

A highly enantioselective aza-Morita-Baylis-Hillman (aza-MBH) reaction of isatin-derived ketimines with acrolein was established using β-isocupreidine (β-ICD) or α-isocupreine (α-ICPN) as a chiral acid-base organocatalyst. The present protocol readily furnished (S) or (R)-aza-MBH adducts with a chiral tetrasubstituted carbon stereogenic center in up to 98% ee.

Asymmetric synthesis of tetrahydropyridines via an organocatalytic one-pot multicomponent Michael/aza-Henry/cyclization triple domino reaction

A low loading of a quinine-derived squaramide efficiently catalyzes the triple-domino Michael/aza-Henry/cyclization reaction between 1,3-dicarbonyl compounds, β-nitroolefins, and aldimines to provide tetrahydropyridines bearing three contiguous stereogenic centers in good yields, excellent enantiomeric excesses, and up to high diastereomeric ratios.

P-chirogenic organocatalysts: application to the aza-Morita-Baylis-Hillman (aza-MBH) reaction of ketimines

The P-chirogenic organocatalysts were found to promote the enantioselective aza-Morita-Baylis-Hillman reaction of ketimines derived from acyclic α-keto esters. In the P-chirogenic organocatalyzed aza-MBH reactions, α,α-disubstituted α-amino acid derivatives were obtained in high yields with high enantioselectivities (up to 97% ee).

The highly enantioselective catalytic aza-Morita–Baylis–Hillman reaction

Chiral phosphine, amine or metal catalyzed asymmetric aza-MBH reactions of various imines with different Michael acceptors in recent decades have been discussed and the perspectives offered by these new developments have also been demonstrated.