Direct Catalytic Asymmetric Doubly Vinylogous Michael Addition of α,β-Unsaturated γ-Butyrolactams to Dienones

Dual Photoredox/Nickel Catalysis Enables Diastereoselective Synthesis of Multisubstituted γ-Lactams Using Alkyl-GeMe3 as Radical Precursors

Herein, we report a single-step, multicomponent approach to versatile γ-lactams through dual photoredox/nickel-catalyzed dicarbofunctionalization of α,β-unsaturated γ-butyrolactam. This reaction utilized alkyl trimethylgermanium as a radical precursor and acyl chloride as the electrophile, demonstrating remarkable functional group compatibility.

Helical polyisocyanide-based macroporous organic catalysts for asymmetric Michael addition with high efficiency and stereoselectivity

Porous materials have attracted interest due to their high specific surface area and rich functionality. Immobilizing organocatalysts onto porous polymers not only boosts enantioselectivity but also improves the reaction rates. In this work, a series of porous polymers C-poly-3ms with rigid polyisocyanide-carrying secondary amine pendants as building blocks were successfully prepared. And the pore size and optical activity of C-poly-3ms can be controlled by the length of the polyisocyanide blocks due to their rigid and helical backbone. C-poly-3150 demonstrated a preferred left-handed helix with a θ 364 value of -8.21 × 103. The pore size and S BET of C-poly-3150 were 17.52 nm and 7.98 m2 g-1, respectively. The porous C-poly-3150 catalyzes the asymmetric Michael addition reaction efficiently and generates the target products in satisfactory yield and excellent enantioselectivity. For 6ab, an enantiomeric excess (ee) and a diastereomeric ratio (dr) up to 99% and 99/1 could be achieved, respectively. The recovered catalyst can be recycled at least 6 times in the asymmetric Michael addition reaction while maintaining activity and stereoselectivity.

Asymmetric Organocatalytic 1,3-Dipolar Cycloaddition of Azomethine Ylides with β-Substituted Cyclic Enones

The enantioselective and diastereoselective control of 1,3-dipolar cycloaddition reactions to β-substituted cyclic enones has been developed. The 1,3-dipolar cycloaddition of phthalazinium dicyanomethanides with cyclic dienones affords chiral tetrahydropyrrolo[2,1-a]phthalazine derivatives 3 through vinylogous iminium ion activation by combining a cinchona-based primary amine C3 and a chiral camphorsulfonic acid additive. Conversely, with a weaker 3,5-bis(trifluoromethyl)benzoic acid additive, the 1,3-dipolar cycloaddition of phthalazinium dicyanomethanides with β-substituted cyclic enones leads to chiral hexahydroisoindolo[1,2-a]phthalazin-10(8H)-one derivatives 4 with excellent stereocontrol via endo-dienamine activation.

Cu-Catalyzed Asymmetric Kinetic Boron Conjugate Addition of γ-Substituted α,β-Unsaturated γ-Lactams

Chiral α,β-unsaturated γ-lactams bearing simple γ- substituents are found in biologically active molecules and natural products, however, their synthesis still remains difficult. Herein, we report an efficient kinetic resolution (KR) of γ-substituted α,β-unsaturated γ-lactams via a Cu-catalyzed asymmetric boron conjugate addition, which also leads to the efficient synthesis of chiral β-hydroxy-γ-lactams with β,γ-stereogenic carbon centers. The KR proceeded smoothly with a wide range of γ-alkyl or aryl substituted substrates including those bearing aromatic heterocycles and different N-protected substrates in up to 347 of s value. Their highly versatile transformations, synthetic utility in biologically active molecules, and inhibitory activities against cisplatin-sensitive ovarian cancer cell A2780 have also been demonstrated. Differing from the well-known mechanism involving Cu-B species in Cu-catalyzed boron conjugate additions, our mechanistic studies using density functional theory (DFT) calculations and experiments indicate that a Lewis acid CuI -catalyzed mechanism is the likely pathway in the catalytic reaction.

Design and development of intramolecular doubly vinylogous Michael addition to access 3-aryl substituted 2-alkenyl-benzofurans and -indoles

Herein, we have disclosed a rare example of an intramolecular doubly vinylogous Michael addition (DVMA). The reaction design exploits the innate reactivity of ortho-heteroatom substituted para-quinone methide (p-QM) derivatives. The sequential reaction of p-QMs and activated allyl halides proceeds through heteroatom-allylation, DVMA and oxidation to furnish a diverse range of 2-alkenyl benzofuran and 2-alkenyl indole derivatives in high yields.

Organocatalyzed Enantioselective Aza-Morita-Baylis-Hillman Reaction of Cyclic Ketimine with α,β-Unsaturated γ-Butyrolactam

The enantioselective aza-MBH reaction is an efficient strategy for constructing novel carbon-carbon bonds, providing access to multitudinous chiral densely functionalized MBH products. However, the enantioselective aza-MBH reaction of cyclic-ketimines that would generate a versatile synthon is still missing and challenging. Herein, we developed a challenging direct organocatalytic asymmetric aza-MBH reaction involving cyclic ketimines attached to a neutral functional group. Moreover, the α,β-unsaturated γ-butyrolactam was utilized as a rare nucleophile alkene in this work. The reactions provide enantiomerically enriched 2-alkenyl-2-phenyl-1,2-dihydro-3H-indol-3-ones, bearing with a tetra-substituted stereogenic center. Moreover, this reaction features high α-selectivities, high enantioselectivities (up to 99% ee), and good yields (up to 80%).

Highly regioselective synthesis of lactams via cascade reaction of α,β-unsaturated ketones, ketoamides, and DBU as a catalyst

Herein, the aldol/Michael cascade reaction on the β,γ-positions of α,β-unsaturated ketones with ketoamides to construct bicyclic lactams via DBU catalysis has been developed. The substrates were well-tolerated with high regio- and diastereoselectivities in moderate to good yields (32 examples). The control experiments revealed that the hydrogen of the amide was the key factor.

Umpolung Asymmetric 1,5-Conjugate Addition via Palladium Hydride Catalysis

Electronically matched nucleophilic 1,6-conjugate addition has been well studied and widely applied in synthetic areas. In contrast, nucleophilic 1,5-conjugate addition represents an electronically forbidden process and is considered unfeasible. Here, we describe modular protocols for 1,5-conjugate addition reactions via palladium hydride catalysis. Both palladium and synergistic Pd/organocatalyst systems are developed to catalyze 1,5-conjugate reaction, followed by inter- or intramolecular [3+2] cyclization. A migratory 1,5-addition protocol is established to corroborate the feasibility of this umpolung concept. The 1,5-addition products are conveniently transformed into a series of privileged enantioenriched motifs, including polysubstituted tetrahydrofuran, dihydrofuran, cyclopropane, cyclobutane, azetidine, oxetane, thietane, spirocycle and bridged rings. Preliminary mechanistic studies corroborate the involvement of palladium hydride catalysis.

Enantioselective direct vinylogous Michael addition for constructing enantioenriched γ,γ-dialkyl substituted butyrolactams and octahydroindoles

A nickel(II)-catalyzed asymmetric direct vinylogous Michael addition of γ-alkyl monosubstituted α,β-unsaturated butyrolactams to α,β-unsaturated carbonyl compounds has been disclosed, affording γ,γ-dialkyl substituted butyrolactams in good yields and satisfactory enantioselectivities. A tandem catalytic asymmetric vinylogous Michael addition/intramolecular Michael addition has also been developed based on this reaction, which enabled the construction of enantioenriched octahydroindoles with three consecutive stereogenic carbon centers.

Recent development in asymmetric organocatalytic domino reactions involving 1,6-addition as a key step

This article highlights the significant development in stereoselective domino reactions involving 1,6-addition as a crucial step.

Enantioselective H-bond-directed vinylogous iminium ion strategy for the functionalization of vinyl-substituted heteroaryl aldehydes

In this work the first H-bond-directed vinylogous iminium ion strategy has been developed as a convenient strategy for the γ,δ-functionalization of vinyl-substituted heteroaromatic aldehydes. Their reaction with α-mercaptoketones proceeds in a cascade manner involving 1,6-addition followed by intramolecular aldol reaction. Excellent stereoselectivities have been obtained as a result of the H-bond interactions controlling the outcome of the cyclization step. The application of the strategy for the synthesis of tricyclic compounds bearing furan, tetrahydrothiophene and dihydropyran moieties has also been demonstrated.

Regioselective and diastereodivergent organocatalytic asymmetric vinylogous Michael addition

Regioselective and diastereodivergent γ-position asymmetric vinylogous Michael addition (AVMA) of cyclohex-2-enones to nitroalkenes and γ′-AVMA between cyclohex-3-enones and nitroalkenes.

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

The principle of vinylogy states that the electronic effects of a functional group in a molecule are possibly transmitted to a distal position through interposed conjugated multiple bonds. As an emblematic case, the nucleophilic character of a π-extended enolate-type chain system may be relayed from the legitimate α-site to the vinylogous γ, ε, ..., ω remote carbon sites along the chain, provided that suitable HOMO-raising strategies are adopted to transform the unsaturated pronucleophilic precursors into the reactive polyenolate species. On the other hand, when "unnatural" carbonyl ipso-sites are activated as nucleophiles (umpolung), vinylogation extends the nucleophilic character to "unnatural" β, δ, ... remote sites. Merging the principle of vinylogy with activation modalities and concepts such as iminium ion/enamine organocatalysis, NHC-organocatalysis, cooperative organo/metal catalysis, bifunctional organocatalysis, dicyanoalkylidene activation, and organocascade reactions represents an impressive step forward for all vinylogous transformations. This review article celebrates this evolutionary progress, by collecting, comparing, and critically describing the achievements made over the nine year period 2010-2018, in the generation of vinylogous enolate-type donor substrates and their use in chemical synthesis.

Asymmetric vinylogous Michael addition of 5-substituted-furan-2(3H)-ones to an α,β-unsaturated-γ-lactam

Asymmetric vinylogous Michael addition involving an α,β-unsaturated-γ-lactam as an acceptor is described.

Primary amine catalyzed diastereo- and enantioselective Michael reaction of thiazolones and α,β-unsaturated ketones

The chiral primary amine catalyzed asymmetric Michael reaction of thiazolones and α,β-unsaturated ketones was reported. Two different optimal catalytic systems were obtained corresponding to cyclic and linear α,β-unsaturated ketones. By employing chiral primary amines as the catalysts and amino-acid derivatives as the additives, a variety of Michael adducts containing the scaffold of the thiazole ring were prepared in moderate to good yields and with excellent diastereo- and enantioselectivities (up to 95% yield, all up to >19/1 dr, up to 96% ee). The reaction was scaled up to obtain 1.73 grams of the Michael adduct with the maintenance of yield and stereoselectivity.

Synthesis of (E,E)-Dienones and (E,E)-Dienals via Palladium-Catalyzed γ,δ-Dehydrogenation of Enones and Enals

A new strategy for the synthesis of conjugated (E,E)-dienones and (E,E)-dienals via a palladium-catalyzed aerobic γ,δ-dehydrogenation of enones and enals has been developed. The method can be employed in the direct and efficient synthesis of various (E,E)-dienones and (E,E)-dienals, including non-substituted α-, β-, and γ- and/or δ-substituted (E,E)-dienones and (E,E)-dienals. The protocol is featured by the ready accessibility and elaboration of the starting materials, good functional group compatibility, and mild reaction conditions. Furthermore, the reaction is of complete E,E-stereoselectivity and uses molecular oxygen as the sole clean oxidant.

Organocatalytic asymmetric spirocyclization reactions of cyclic 2,4-dienones with cyanoketones: synthesis of spiro-dihydropyrano cyclohexanones

The first organocatalytic asymmetric synthesis of spiro-dihydropyrano cyclohexanones has been developed via the cascade reaction between cyanoketones and cyclic 2,4-dienones. A cinchona alkaloid-derived bifunctional primary amine catalyst in combination with N-Boc-tleucine was found to be the most effective for this spirocyclization reaction and provided the desired products in moderate to good yields with high enantioselectivities.

One-Pot Allylation-Intramolecular Vinylogous Michael Addition-Isomerization Cascade of o-Hydroxycinnamates and Congeners: Synthesis of Substituted Benzofuran Derivatives

A unique intramolecular vinylogous Michael addition leading to the synthesis of heterocycles has been disclosed. Base-promoted one-pot sequential O-allylation of o-hydroxy-cinnamates or -cinnamonitrile or -chalcones with γ-bromocrotonates followed by an intramolecular conjugate addition of vinylogous Michael donors resulted in the formation of highly substituted benzofuran derivatives in good to excellent yields. The intramolecular event followed by two [1,3]-H shifts leading to aromatization appears to be the key to the success of this unprecedented transformation.

Asymmetric domino 1,6-addition/annulation reaction of 3-cyano-4-alkenyl-2H-chromen-2-ones with isatin-derived MBH carbonates: enantioselective synthesis of 3,3′-cyclopentenylspirooxindoles bearing 2H-chromen-2-ones

An asymmetric domino 1,6-addition/annulation reaction of 3-cyano-4-alkenyl-2H-chromen-2-ones with isatin-derived MBH carbonates was achieved by using a modified cinchona alkaloid as a catalyst.

A chiral-at-metal asymmetric catalyzed vinylogous Michael addition of ortho-methyl aromatic nitro compounds for isoxazole derivative synthesis

A chiral-at-metal rhodium(iii) complex catalyzed asymmetric vinylogous Michael addition of 5-methyl 4-nitroisoxazoles with α,β-unsaturated 2-acyl imidazoles has been developed, delivering the corresponding adducts with up to 96% yield and 97% ee.

Asymmetric synthesis of highly functionalized furanones via direct Michael reactions mediated by a bulky primary amine

A bulky chiral primary amine catalyzed Michael reaction of 3(2H)-furanones has been realized, leading to the construction of substituted furanone derivatives.

A vinylogous Michael addition-triggered quadruple cascade reaction for the enantioselective generation of multiple quaternary stereocenters

An efficient organocatalytic vinylogous Michael addition-triggered quadruple cascade reaction resulting in fused spiroxindoles bearing multiple quaternary stereocenters is demonstrated from β-trifluoroacetylarylidene indanediones and 3-alkylideneoxindoles.

Organocatalytic asymmetric Michael addition between 3-subsituted oxindoles and enals catalyzed by camphor sulfonyl hydrazine

3,3-Disubstituted oxindoles containing vicinal stereogenic carbon centers have been synthesized through organocatalytic asymmetric Michael addition between 3-substituted oxindoles and enals catalyzed by chiral camphor sulfonyl hydrazines (CaSHs).

Highly enantioselective sequential vinylogous aldol reaction/transesterification of methyl-substituted olefinic butyrolactones with isatins for the construction of chiral spirocyclic oxindole-dihydropyranones

A highly stereoselective sequential vinylogous aldol reaction/transesterification of methyl-substituted olefinic butyrolactones and isatins was developed with 10 mol% Takemoto's amine–thiourea catalyst.

Direct β-selectivity of α,β-unsaturated γ-butyrolactam for asymmetric conjugate additions in an organocatalytic manner

The β-selective asymmetric addition of γ-butyrolactam with cyclic imino esters catalyzed by a bifunctional chiral tertiary amine has been developed, which provides an efficient access to optically active β-position functionalized pyrrolidin-2-one derivatives in both high yield and enantioselectivity (up to 78% yield and 95 : 5 er). This is the first catalytic method to access chiral β-functionalized pyrrolidin-2-one via a direct organocatalytic approach.

Regiospecific 1,4-Michael Addition of Phenylacetonitrile to 1,5-Diarylpenta-2,4-Dien-1-Ones

The regiospecific 1,4-Michael addition of phenylacetonitrile to (2E,4E)-1,5-diarylpenta-2,4-dien-1-ones produced 12 novel (E)-3-(2-oxo-2-arylethyl)-2,5-diarylpent-4-enenitriles in 77-88% yield. The advantages of the method are broad substrate scope, mild conditions, good to high yields and high selectivity. The method can also be extended to a gram scale.