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

Diastereo- and Enantioselective Synthesis of Highly Functionalized Tetrahydropyridines by Recyclable Novel Bifunctional C2-Symmetric Ionic Liquid–Supported (S)-Proline Organocatalyst

An efficient, novel bifunctional C2-symmetric ionic liquid–supported (S)-proline organocatalyst 7 was developed for a one-pot, five-component reaction involving β-keto esters 8, aryl aldehydes 9, and aryl amines 10, affording highly functionalized tetrahydropyridines 11a–o by simultaneous generation of fives bonds and two stereogenic centers with extraordinary diastereo- and enantioselectivities (up to >99:1 dr, 95:5 er) in isopropanol with high yields (up to 92%). This protocol provides quick access to diverse enantio-enriched, highly functionalized diastereo- and enantioselective tetrahydropyridines in a green medium without any column chromatographic purification. The catalyst was recycled five times without significant loss of its catalytic activity.

A novel isosteviol-based bifunctional squaramide organocatalyst for enantioselective Michael addition of acetylacetone to nitroolefins

Chiral amine-squaramide is a kind of effective hydrogen bond donor bifunctional catalyst to promote many asymmetric transformations. In this paper, novel chiral tertiary amine-squaramide derived from the natural product of the stevioside was developed and applied into the asymmetric Michael addition of acetylacetone to nitroolefins. This asymmetric reaction performed well, and a series of enantiomerically enriched compounds were obtained in high yields (up to 96%) with excellent enantioselectivities (up to 99% ee).

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.

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.

Enantioselective Reaction between 2-(Cyanomethyl)azaarenes and N-Boc-amino Sulfones

A series of 2-(cyanomethyl)azaarenes containing benzothiazole or benzoxazole were designed and synthesized for asymmetric α-functionalization with N-Boc-amino sulfones. The Mannich adducts were obtained in high yields with good diastereo- and enantioselectivities. Aryl-substituted amino sulfones were tolerated under the current conditions, and the reaction can be performed on gram scale in good results.

Organocatalytic Asymmetric Cascade Reactions Based on Gamma-Nitro Carbonyl Compound

The significant advancements in asymmetric organocascade reactions have been accomplished during the past decades, paving the way to the efficient and stereoselective construction of structurally complex scaffolds from simple and readily available starting materials. Nitro-containing cyclic compounds have become a privileged molecular library given their broad and promising activities in various therapeutic areas. In various approaches to build these valuable scaffolds, the utility of γ-nitrocarbonyl intermediates is one of the most efficient approaches due to its high efficiency, reliability and versatility. The strategies and catalyst systems described here highlight recent advances in the enantioselective synthesis of nitro-containing cyclic molecules via organocascade strategies based on γ-nitrocarbonyl intermediates. Various organocatalysts with distinct activation modes have found application in providing these sophisticated compounds. This review is organized according to the types of organocatalyst. These methods are of importance for the construction of complex chiral cyclic frameworks and the design of new pharmaceutical compounds. We believe that compounds based on nitro-containing cyclic skeletons have the potential to provide novel therapeutic agents and useful biological tools.

C(sp3)–H dehydrogenation and C(sp2)–H alkoxy carbonylation of inactivated cyclic amines towards functionalized N-heterocycles

A novel and efficient synthesis of tetrahydropyridine-, dihydropyrrole-, and tetrahydroazepine-3-carboxylates via cascade reactions of cyclic amines with CO and alcohols is presented. To our knowledge, this should be the first example in which functionalized N-heterocycles were prepared through Pd-catalyzed C(sp³)–H dehydrogenation and C(sp²)–H carbonylation of cyclic amines.

BF3·Et2O mediated one-step synthesis of N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines

A simple and efficient one-pot ring annulation provides quick access to N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines.

TiCl2·2H2O catalyzed one-pot synthesis of highly functionalized tetrahydropiperidines and evaluation of their antimicrobial activities

One-pot condensation reaction of ethyl acetoacetate, various substituted benzaldehydes and anilines in the presence of TiCl

Intramolecular Lewis pairs with two acid sites – reactivity differences between P- and N-based systems

Unlike the aniline PhN[(CH₂)₃B(C₆F₅)₂]₂ the doubly hydroborated species (^tBu/Ph)P[(CH₂)₃B(C₆F₅)₂]₂ show no dynamic exchange of the boron Lewis acid functions in solution and are not catalytically active in terms of H/D-scrambling as well as hydrogenation reactions.

Recent developments in multicomponent synthesis of structurally diversified tetrahydropyridines

Tetrahydropyridines (THPDs) have recognized as a major constituent of naturally occurring alkaloids and exhibits various biological and pharmacological profiles. For their synthesis, MCRs are employed as an excellent tool to generate vast libraries.

Enantioselective synthesis of chiral α,β-unsaturated γ-substituted butyrolactams by organocatalyzed direct asymmetric vinylogous Michael addition of α,β-unsaturated γ-butyrolactam to 2-enoylpyridines

Approach providing a series of optically active α,β-unsaturated γ-substituted butyrolactams in high yields with excellent diastereo- and enantioselectivities.

Asymmetric synthesis of 3,3′-pyrrolidinyl-dispirooxindoles via a one-pot organocatalytic Mannich/deprotection/aza-Michael sequence

A highly stereoselective synthesis of functionalized 3,3′-pyrrolidinyl-dispirooxindole derivatives with three stereogenic centers, including two contiguous spiro-stereocenters, has been achieved through an organocatalytic Mannich/Boc-deprotection/aza-Michael sequence.

Novel Chiral Bifunctional L-Thiazoline-Thiourea Derivatives: Design and Application in Enantioselective Michael Reactions

Several novel chiral bifunctional L-thiazoline-thiourea derivatives were easily synthesized from commercially available L-cysteine in high yield. These catalysts were subsequently applied to the enantioselective Michael addition of acetylacetone to β-nitrostyrenes. The products with S configuration were obtained in 98% enantiomeric excess (ee) when the L-thiazoline-thiourea derivatives were used. A plausible transition state model is proposed to explain the observed enantioselectivities.

Highly Enantioselective Cascade Reaction Catalyzed by Squaramides: the Synthesis of CF3-Containing Chromanes

A catalytic asymmetric method for the synthesis of 2-CF3 chromanes has been described. Generally, the squaramide-catalyzed cascade reaction of 2-hydroxychalcones with β-CF3-nitroalkenes gave the CF3-containing heterocyclic compounds bearing three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities.

Enantioselective Synthesis of Functionalized Polycarbocycles via a Three-Component Organocascade Quadruple Reaction

An efficient organocascade quadruple reaction was conducted to synthesize a functionalized spiropolycyclic scaffold in high chemical yields (43-80%) and excellent levels of stereoselectivity (up to >19:1 dr and 99% ee). The quadruple reaction proceeded smoothly between 1,3-indanedione and aromatic aldehydes with concomitant desymmetrization of prochiral 4-substituted cyclohexanones through the Knoevenagel/Michael/aldol/aldol reaction sequence catalyzed by a bifunctional thiourea catalyst. Two of the formed products were transformed into spirocyclic epoxides containing four contiguous quaternary centers.

Organocatalytic Asymmetric Domino Michael/Henry Reaction of Indolin-3-ones with o-Formyl-β-nitrostyrenes

A highly diastereo- and enantioselective domino Michael/Henry reaction of 1-acetylindolin-3-ones with o-formyl-(E)-β-nitrostyrenes catalyzed by low loading of a quinine-derived amine-squaramide provides the corresponding indolin-3-one derivatives bearing four adjacent stereogenic centers in good to high yields and with excellent stereoselectivities.

Recyclable organocatalyst-promoted one-pot Michael/aza-Henry/lactamization reactions for fluorinated 2-piperidinones bearing four stereogenic centres

A highly efficient method for asymmetric synthesis of fluorinated 2-piperidinones bearing four stereogenic centres is introduced.