Vinylogous and Arylogous Stereoselective Base-Promoted Phase-Transfer Catalysis

Vinylogous enolate and enolate-type carbanions, generated by deprotonation of α,β-unsaturated compounds and characterized by delocalization of the negative charge over two or more carbon atoms, are extensively used in organic synthesis, enabling functionalization and C–C bond formation at remote positions. Similarly, reactions with electrophiles at benzylic and heterobenzylic position are performed through generation of arylogous and heteroarylogous enolate-type nucleophiles. Although widely exploited in metal-catalysis and organocatalysis, it is only in recent years that the vinylogy and arylogy principles have been translated fruitfully in phase-transfer catalyzed processes. This review provides an overview of the methods developed to date, involving vinylogous and (hetero)arylogous carbon nucleophiles under phase-transfer catalytic conditions, highlighting main mechanistic aspects.

Rational drug design, synthesis, and biological evaluation of novel chiral tetrahydronaphthalene-fused spirooxindole as MDM2-CDK4 dual inhibitor against glioblastoma

Simultaneous inhibition of MDM2 and CDK4 may be an effective treatment against glioblastoma. A collection of chiral spirocyclic tetrahydronaphthalene (THN)-oxindole hybrids for this purpose have been developed. Appropriate stereochemistry in THN-fused spirooxindole compounds is key to their inhibitory activity: selectivity differed by over 40-fold between the least and most potent stereoisomers in time-resolved FRET and KINOMEscan® in vitro assays. Studies in glioblastoma cell lines showed that the most active compound ent-4g induced apoptosis and cell cycle arrest by interfering with MDM2 -P53 interaction and CDK4 activation. Cells treated with ent-4g showed up-regulation of proteins involved in P53 and cell cycle pathways. The compound showed good anti-tumor efficacy against glioblastoma xenografts in mice. These results suggested that rational design, asymmetric synthesis and biological evaluation of novel tetrahydronaphthalene fused spirooxindoles could generate promising MDM2-CDK4 dual inhibitors in glioblastoma therapy.

Recent synthetic strategies toward the synthesis of spirocyclic compounds comprising six-membered carbocyclic/heterocyclic ring systems

Spirocyclic compounds fascinate the synthetic chemists due to their privileged ring system and efficacy in drug discovery. Many natural compounds comprise spirocyclic moiety in their skeleton and are effective in pharmaceutical industry. Over the years, many synthetic methodologies have been established for the construction of spirocyclic compounds. In this review, recent synthetic approaches to accessing various spirocompounds comprising six-membered carbocycles/heterocycles have been summarized.

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.

Copper-catalyzed asymmetric tandem borylative addition and aldol cyclization

A highly enantioselective asymmetric copper-catalyzed tandem conjugate addition/aldol cyclization of electron-deficient olefins with B₂pin₂ was developed, which provided a rapid access to indanes bearing three consecutive chiral stereogenic centers.

Protecting group-directed annulations of tetra-substituted oxindole olefins and sulfur ylides: regio- and chemoselective synthesis of cyclopropane- and dihydrofuran-fused spirooxindoles

Protecting group-controlled regio- and chemoselective synthesis of cyclopropane- and dihydrofuran-fused spirooxindoles containing vicinal quaternary carbon centers.

Iron-Catalyzed Synthesis of Tetrahydronaphthalenes via 3,4-Dihydro-2H-pyran Intermediates

The development of an iron(III)-catalyzed synthetic strategy toward functionalized tetrahydronaphthalenes is described. This approach is characterized by its operational simplicity and is distinct from currently available procedures that rely on [4 + 2]-cycloadditions. Our strategy takes advantage of the divergent reactivity observed for simple aryl ketone precursors to gain exclusive access to tetrahydronaphthalene products (23 examples). Detailed mechanistic investigations identified pyrans as reactive intermediates that afford the desired tetrahydronaphthalenes in high yields upon iron(III)-catalyzed Friedel-Crafts alkylation.

Drug design based on pentaerythritol tetranitrate reductase: synthesis and antibacterial activity of Pogostone derivatives

We performed molecular docking studies of Pogostone with PETNR and analyzed structure–activity relationships, which guided the structure design and the subsequent facile organocatalytic synthesis of Pogostone derivatives.

Direct N–H/α,α,β,β-C(sp3)–H functionalization of piperidine via an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles

A protocol for the direct functionalization of N–H/α,α,β,β-C(sp³)–H of piperidine without any metal or external oxidants is reported.