A base-free and acceptorless Ru-catalyzed dehydrogenative approach has been developed for the synthesis of N-heterocycles by using 1,3-dicarbonyls and amino alcohols through a domino sequential enamine formation and intramolecular oxidative cyclization strategy. This unified approach is also applicable for the synthesis of O-heterocycles involving 2-hydroxybenzyl alcohol as a coupling reactant via consecutive C-alkylation and intramolecular cyclization steps. The present protocol is general for the synthesis of varieties of biologically important scaffolds, such as tetrahydro-4H-indol-4-one, 3,4-dihydroacridin-1­(2H)-one, and tetrahydro-1H-xanthen-1-ones derivatives using a single catalytic system, viz. RuH2CO­(PPh3)3. Environmentally benign H2O and H2 are the only byproducts in this domino process. Moreover, RuH2CO­(PPh3)3-catalyzed C3-alkylation of tetrahydro-4H-indol-4-one using alcohol as a alkylating partner is also described in this report. For the first time, a solvent-free gram-scale reaction for the acceptorless dehydrogenative annulation has been demonstrated. A plausible mechanism for the Ru-catalyzed base-free and acceptorless dehydrogenative annulation of amino alcohols or 2-hydroxybenzyl alcohols has been provided with several experimental investigations and spectroscopic evidence.

We have demonstrated the magnetically retrievable Fe(OH)3Fe3O4catalyzed C–H peroxidation of 2-oxindole and barbituric acid derivatives under batch and continuous flow process for the first time.

Ru(ii)-NHC catalyzes α-olefination of 2-oxindoles using diaryl methanols in the absence of an acceptor. A wide array of symmetrical and unsymmetrical diaryl methanols undergoes dehydrogenative coupling with 2-oxindole selectively to generate various substituted 3-(diphenylmethylene)indolin-2-one derivatives in good yields and produces environmentally benign by-products, H2 and H2O. This methodology was successfully applied for the synthesis of a bioactive drug i.e. TAS-301. The biological activities of the synthesized 3-(diphenylmethylene)indolin-2-one derivatives were screened against the Plasmodium falciparum parasite and found to exhibit a significant activity with IC50 = 2.24 μM.

Herein, we report a highly chemoselective and efficient heterogeneous MnO2@Fe3O4 MNP catalyst for the oxidation of benzylic sp3 C−H group of ethers using TBHP as a green oxidant to afford ester derivatives in high yield under batch/continuous flow module. This catalyst was also effective for the benzylic sp3 C−H group of methylene derivatives to furnish the ketone in high yield which can be easily integrated into continuous flow condition for scale up. The catalyst is fully characterized by spectroscopic techniques and it was found that 0.424 % MnO2@Fe3O4 catalyzes the reaction; the magnetic nanoparticles of this catalyst could be easily recovered from the reaction mixture. The recovered catalyst was recycled for twelve cycles without any loss of the catalytic activity. The advantages of MnO2@Fe3O4 MNP are its catalytic activity, easy preparation, recovery, and recyclability, gram scale synthesis with a TOF of up to 14.93 h−1 and low metal leaching during the reaction.

An environmentally benign approach for the bioactive tetraketones using epoxides and cyclic-1,3-diketones in the presence of Fe-zeolite as a catalyst via Meinwald rearrangement has been developed under batch and continuous...