Diastereoselective Formal 1,3-Dipolar Cycloaddition of Trifluoroethyl Amine-Derived Ketimines Enables the Desymmetrization of Cyclopentenediones

In this research, a metal-free diastereoselective formal 1,3-dipolar cycloaddition of N-2,2,2-trifluoroethylisatin ketimines and cyclopentene-1,3-diones which can efficiently lead to the desymmetrization of cyclopentene-1,3-diones is developed. With the developed protocol, a series of tetracyclic spirooxindoles containing pyrrolidine and cyclopentane subunits can be smoothly obtained with good results (up to 99% yield and 91:9 dr). Furthermore, the methodology can be extended to trifluoromethyl-substituted iminomalonate, and the corresponding formal [3+2] cycloaddition reaction affords bicyclic heterocycles containing fused pyrrolidine and cyclopentane moieties in moderate yields with >20:1 dr. The synthetic potential of the methodology is demonstrated by the scale-up experiment and by versatile transformations of the products.

Efficient Synthesis of 2,3'-Spirobi (Indolin)-2'-Ones and Preliminary Evaluation of Their Damage to Mitochondria in HeLa Cells

A novel formal (4 + 1) annulation between N-(o-chloromethyl)aryl amides and 3-chlorooxindoles through in situ generated aza-ortho-QMs with 3-chlorooxindoles is reported for the synthesis of a series of 2,3'-spirobi (indolin)-2'-ones in high yields. Under structured illumination microscopy, compound 3a is found to change the mitochondrial morphology and induce mitophagy pathway, which might then trigger mitophagy in cancer cells.

Dinuclear zinc-catalyzed enantioselective formal [3 + 2] cycloaddition of N-2,2,2-trifluoroethylisatin ketimines with low reactivity aurone derivatives

Highly enantioselective formal [3 + 2] cycloaddition of N-2,2,2-trifluoroethylisatin ketimines with aurone derivatives of low reactivity using chiral dinuclear zinc catalysts has been developed via a Brønsted base and Lewis acid cooperative activation model. These transformations involving a domino Michael/Mannich reaction sequence led to efficient construction of a range of chiral spiro[benzofuran-pyrrolidine] scaffolds bearing three biologically relevant heterocyclic moieties and two adjacent spiro quaternary stereocenters in high yields (up to 95%) and with good enantioselectivities (up to 99% ee).

Organocatalytic synthesis of chiral CF3-containing oxazolidines and 1,2-amino alcohols: asymmetric oxa-1,3-dipolar cycloaddition of trifluoroethylamine-derived azomethine ylides

A series of CF₃-containing oxazolidines were constructed via organocatalytic asymmetric oxa-1,3-dipolar cycloaddition. These oxazolidines could undergo facile conversion to CF₃-containing 1,2-amino alcohols with vicinal stereogenic centers.

H-bonding vs Protonation of Alkynes in Regioselective Hydroamination Reactions: A Glimpse into the Reactivity of Arylogous Ynolethers and Ynamines

In this paper is described the competition and transition between hydrogen bonding and protonation of alkynes connected, on one side, to various aromatic rings and to chiral amino ester appendages on the other side. While the first mode of activation induced the cyclization into pyrrolidines, the protonation of the alkyne led preferentially to tetrahydropyridines due to the higher level of the highest occupied molecular orbital (HOMO) of the considered arylogous ynolethers and ynamines. The transition between H-bonding and protonation was observed with the alkyne substituted with 2-methoxyphenyl, for which the cyclization delivered either five- or six-membered rings depending on the temperature of the experiment. From there, the cyclization of dialkoxy- and trialkoxyphenyl-substituted alkynes into six-membered rings, i.e., tetrahydropyridines, was developed. When next applied to alkynylindoles, the same pattern of cyclization provided six-membered rings as an illustration of the reactivity of arylogous ynamines. Thanks to the high reactivity of the intermediate cationic species, weak nucleophiles such as NH-oxazolidinone participated efficiently in the hydroamination reaction of alkynylindoles. Pyrrolidines, tetrahydropyridines, and piperidines decorated with various aromatics and substituents were thus prepared in enantio- and stereoselective manner. Capitalizing on the enamine moiety of the azaheterocycles, the molecular diversity was extended through stereoselective oxidation and ring contraction processes.

The asymmetric construction of CF3-containing spiro-thiazolone-pyrrolidine compoundsvia[3 + 2] cycloaddition

An organocatalytic method for the asymmetric construction of CF₃-containing spiro-thiazolone-pyrrolidine compounds has been developed.

Insights into the mechanisms of Ag-catalyzed synthesis of CF3-substituted heterocycles via [3+2]-cycloaddition from α-trifluoromethylated methyl isocyanides: effects of DBU and exploration of diastereoselectivity

The diastereoselectivity of [3+2]-cycloaddition can be reasonably explained by the analysis of steric hindrance using DFT calculations.

Highly efficient enantioselective synthesis of bispiro[benzofuran-oxindole-pyrrolidine]s through organocatalytic cycloaddition

The first organocatalyzed [3 + 2] cyclisation of N-2,2,2-trifluoroethylisatin ketimines with aurones has been developed.

Organocatalytic asymmetric synthesis of highly substituted pyrrolidines bearing a stereogenic quaternary centre at the 3-position

An organocatalytic asymmetric cascade reaction has been developed for the synthesis of highly substituted pyrrolidines having a stereogenic quaternary centre at the 3-position. N-Tosyl aminomethyl enone and trans-α-cyano-α,β-unsaturated ketone were utilized as the reaction partners in this method. Cinchonidine derived bifunctional amino-squaramide catalysts were the best to obtain the products in high enantio- and diastereoselectivities.

Catalytic Asymmetric Mannich Type Reaction with Tri-/Difluoro- or Trichloroacetaldimine Precursors

A highly efficient catalytic asymmetric Mannich type reaction of CF₃-_, CF₂H-, or CCl₃-acetaldimine precursors by a chiral primary amine is presented. This protocol provides facile access to chiral CF₃-, CF₂H-, or trichloroethyl amines in excellent yields and high enantioselectivity (up to 99% yield, up to >99% ee).

Recent Advances in Organocatalyzed Domino C-C Bond-Forming Reactions

Reactions that form a C-C bond make up a foundational pillar of synthetic organic chemistry. In addition, organocatalysis has emerged as an easy, environmentally-friendly way to promote this type of bond formation. Since around 2000, organocatalysts have been used in a variety of C-C bond-forming reactions including Michael and aldol additions, Mannich-type reactions, and Diels-Alder reactions, to name a few. Many of these methodologies have been refined and further developed to include cascade and domino processes. This review will focus on recent advances in this area with an emphasis on methodologies having applications in the synthesis of biologically-significant compounds.

Squaramide-catalyzed domino Michael/aza-Henry [3 + 2] cycloaddition: asymmetric synthesis of functionalized 5-trifluoromethyl and 3-nitro substituted pyrrolidines

The diastereo- and enantioselective Michael/aza-Henry [3 + 2] cycloaddition reaction of trifluoromethyl-substituted iminomalonate and nitroalkenes has been developed employing 10 mol% of a quinine-squaramide catalyst.