Copper-Catalyzed Coupling of Thioamides and Donor/Acceptor-Substituted Carbenoids: Synthesis of Enamino Esters and Enaminones

Catalyst-free reactions of anilines with β-chloroenones: synthesis of α-chloroenaminones and 1,4-benzodiazepines

The Michael addition of anilines to β-chloroenones gives enaminones by the elimination of hydrochloric acid (HCl). These enaminones are transformed into α-chloroenaminones via in situ sp2 C-H functionalization. Anilines that are attached to an electron-donating group react more readily with β-chloroenone to give the corresponding products in excellent yields. A highly atom-economical method has been developed using dimethyl sulfoxide (DMSO) as a green oxidant and solvent. The desired α-functionalized enaminones are formed in good yields with excellent Z-selectivity. We have established the generality of this reaction with many substrates, and scaled-up reactions have been performed to showcase the practical applications. A catalyst-free double annulation of β-chloroenones with o-phenylenediamine has also been demonstrated for the synthesis of 1,4-benzodiazepine derivatives in moderate yields under mild reaction conditions.

Synthesis of Tetrasubstituted Enamines through Borane-Catalyzed Hydrogenations

This paper describes a B(C6F5)3-catalyzed hydrogenation of β-substituted α,β-unsaturated imines by using as low as 0.2 mol % catalyst. A variety of tetrasubstituted enamines were afforded in 95-99% yields. It provides an efficient and facile way without the need for column chromatography purification.

Coupling of acceptor-substituted diazo compounds and tertiary thioamides: synthesis of enamino carbonyl compounds and their pharmacological evaluation

This paper describes the synthesis of enamino carbonyl compounds by the copper(i)-catalyzed coupling of acceptor-substituted diazo compounds and tertiary thioamides. We plan to use this method to synthesize indolizidine (−)-237D analogs to find α6-selective antismoking agents. Therefore, we also performed in silico α6-nAchRs binding studies of selected products. Compounds with low root-mean-square deviation values showed more favorable binding free energies. We also report preliminary pharmacokinetic data on indolizidine (−)-237D and found it to have weak activity at CYP3A4. In addition, as enamino carbonyl compounds are also known for antimicrobial properties, we screened previously reported and new enamino carbonyl compounds for antibacterial, antimicrobial, and antifungal properties. Eleven compounds showed significant antimicrobial activities.

This paper describes the synthesis of enamino carbonyl compounds by the copper(i)-catalyzed coupling of acceptor-substituted diazo compounds and tertiary thioamides.

A solvent controlled three-component reaction of diazo compounds for the synthesis of hydrazone compounds under Brønsted acid catalysis

A novel Brønsted acid catalyzed three-component reaction of diazo compounds has been achieved from α-diazo ester, N-aminophthalimide and a solvent.

Nucleophilic Vinylic Substitution (SNV) of Trisubstituted Monofluoroalkenes for the Synthesis of Stereodefined Trisubstituted Alkenes and Divinyl Ethers

We herein describe a nucleophilic vinylic substitution (S_NV) of trisubstituted monofluoroalkenes with excellent stereocontrol (d.r. > 99:1). Starting from (E)-β-monofluoroacrylates, various trisubstituted (E)-alkenes containing O/N/S-substituent groups at the vinylic position can be obtained under simple conditions. Furthermore, (E,E)-divinyl ethers can be generated through dimerization of the monofluoroalkenes, triggered by adventitious water in the reaction mixture.

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

A highly modular method for the synthesis of (Z)-3-[amino(phenyl/methyl)methylidene]-1,3-dihydro-2H-indol-2-ones starting from easily available 3-bromooxindoles or (2-oxoindolin-3-yl)triflate and thioacetamides or thiobenzamides is described. A series of 49 compounds, several of which have previously been shown to possess significant tyrosin kinase inhibiting activity, was prepared in yields varying mostly from 70 to 97% and always surpassing those obtained by other published methods. The method includes an Eschenmoser coupling reaction, which is very feasible (even without using a thiophile except tertiary amides) and scalable. The (Z)-configuration of all products was confirmed by NMR techniques.

Application of NMR Spectroscopy for the Detection of Equilibrating E-Z Diastereomers

Conjugation can lower the energy barrier for unsaturated C-C bond rotations, resulting in a mixture of equilibrating diastereomers at room temperature. Therefore, methods claiming diastereoselective synthesis of conjugated double bonds often require proof that the observed diastereomeric ratio is not because of the diastereomeric equilibration of the product. Variable-temperature (VT) NMR experiments are commonly used to distinguish between the two possibilities. However, the VT technique requires accessories for the NMR spectrometer and more setup time. Here, we show that the rarely used application of 1-D and 2-D nuclear Overhauser effect spectroscopy experiments for the detection of the equilibrating diastereomers is a convenient alternative to the VT technique.