A novel two-step synthesis of β-trifluoromethyl primary amines from readily available α-(trifluoromethyl)styrenes and phthalimide is developed. The first step involves a hydroamination between α-(trifluoromethyl)styrenes and phthalimide (PhthNH) with the assistance of a base. Next, the hydrazinolysis of the resulting N-(β-trifluoromethyl-β-arylethyl)phthalimides with hydrazine hydrate affords the desired N-(β-trifluoromethyl-β-arylethyl)amines.
A trio of Ir(iii) complexes that are held together by a picolinamidato moiety were created. In our earlier research, we demonstrated the catalytic activity of the complexes for producing alpha-alkylated ketones from a ketone or secondary alcohol with a primary alcohol in the presence of a catalytic amount of a Cp*Ir(iii) catalyst and tBuOK in toluene at 110 °C using the hydrogen-borrowing technique. Earlier many research groups had synthesized quinoline, pyrrole, and pyridine derivatives using 2-amino alcohol and ketone or secondary alcohol derivatives as starting materials, but in all those cases the reaction conditions are not suitable in terms of green synthesis like more catalyst loading, base loading, long reaction time, and high temperature. In addition, most of the reactions contain phosphine a hazardous by-product, along with the catalyst. Keeping in mind these shortcomings, we tried to expand the use of our catalysts after achieving an excellent result in our previous work, and we were successful in producing quinoline, pyrrole, and pyridine derivatives through acceptor-less dehydrogenative coupling (ADC) procedures at 90–110 °C under neat/solvent-free conditions and achieved good to exceptional yields of those nitrogen-containing heterocycles. This methodology is attractive because it is environmentally benign and allows for the “green” synthesis of nitrogen-containing heterocycles. All that is required is a modest quantity of catalyst and base, and the by-products are merely H2O and H2.
Diverse quinazolinone-[2,3]-fused polycyclic skeletons occupy a prominent position in drug discovery. Even with currently available methods there still remain unmet needs for flexible access to such structures. Herein, we have explored a mild “one pot” procedure for the construction of various quinazolinone-[2,3]-fused polycycles. The procedure involves Pd-catalyzed carbonylation of N-(2-iodophenyl)acetamides, release of the masked terminal amine, and two sequential and spontaneous cyclizations. This generally applicable approach features easy assembly of precursors from readily available starting materials, mild reaction conditions, non-cumbersome operation, and polycyclic diversity.
C-3 amidated imidazoheterocycles were synthesized via a visible light-promoted reaction of imidazoheterocycles with N-amidopyridinium salts catalyzed by 4CzIPN under mild conditions. For imidazoheterocycles and N-amidopyridinium salts with various substituents, the reaction proceeded smoothly to give the corresponding products in moderate to good yields. The reaction provides a new strategy for the synthesis of secondary amides with the imidazo[1,2-a]pyridine core.
In this study, we developed a cascade 5,5-cyclisation of internal ketene-N,O-acetals utilizing homogeneous Au(i) catalysis. This process involves an initial 5-exo-dig carbocyclisation, followed by a 5-exo-dig heterocyclisation that stereoselectively incorporates the O-atom of a water molecule into an N-tethered propargyl alkyne. This sequential reaction results in the formation of one C–C, two C–O, and two C–I bonds, ultimately leading to the synthesis of spiro-α-iodo-γ-lactone structures featuring oxazole rings in good yields.
An arylazopyrazole-based covalent inhibitor targeting the mitotic motor protein of centromere-associated protein E (CENP-E) was developed. Using this photoswitchable inhibitor, a photoswitchable CENP-E was chemically constructed in cells, which enabled to local control of mitotic cell division with light illumination.
Palladium-catalyzed synthesis of deoxybenzoin derivatives from styryl ethers and arylboronic acids is reported. The reaction proceeds under mild conditions in the presence of TEMPO and provides the desired products in good to excellent yields. Simple operation, broad substrate scope, and functional group tolerance are the salient features of the developed methodology.
The rapid synthesis of hydrogen bond templated handcuff rotaxanes is described. The isolated rotaxanes were characterized by NMR and IR spectroscopies and high resolution mass spectrometry. This report represents a rare demonstration of preparing (2)handcuff [2]rotaxanes by covalently linking separate axles threaded through the rings of a bis-macrocycle by use of the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction.
Pyridines undergo a facile SNHAr phosphinylation with H-phosphinates under catalyst- and solvent-free conditions (50–55 °C) in the presence of benzoylphenylacetylene to afford 4-phosphinylpyridines in up to 68% yield. In this reaction, benzoylphenylacetylene activates the pyridine ring by the formation of a 1,3(4)-dipolar complex, deprotonates H-phosphinates to generate P-centered anions and finally acts as an oxidizer, being eliminated from an intermediate ion pair. Terminal electron-deficient acetylenes (methyl propiolate and benzoylacetylene) are inefficient as mediators in the above SNHAr process.
A catalyst free ultrasound-assisted regio-/stereoselective modular approach was accomplished for the synthesis of highly constrained indenoquinoxaline engrafted spiro pyrrolidines from easily available substrates. This one-pot strategy utilizes 1,3-dipolar cycloaddition from a four component reaction of ninhydrin, 1,2-phenylenediamine, β-nitrostyrene and benzylamine or amino acids under ultrasound irradiation. The transformation is mild and operationally simple, providing architecturally complex fused spiro polycyclic heterocycles. This synthesis was confined to follow the group-assistant-purification (GAP) chemistry process, which can avoid chromatographic purifications and use of catalysts and allows easy access to a novel class of spiro engrafted polyheterocyclic scaffolds, which may be beneficial in biomedical research/materials science in the near future. This opens an era for the formation of a single exo product, when compared with reported protocols, by merely switching over reaction conditions to US irradiation.
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