DDQ/Fe(NO)-Catalyzed Aerobic Synthesis of 3-Acyl Indoles and an In Silico Study for the Binding Affinity of -Tosyl-3-acyl Indoles toward RdRp against SARS-CoV-2.

In the present study, we herein report a DDQ-catalyzed new protocol for the synthesis of substituted 3-acylindoles. Being a potential system for virtual hydrogen storage, introduction of catalytic DDQ in combination with Fe(NO)·9HO and molecular oxygen as co-catalysts offers a regioselective oxo-functionalization of C-3 alkyl-/aryllidine indolines even with scale-up investigations. Intermediate isolation, their spectroscopic characterization, and the density functional theory calculations indicate that the method involves dehydrogenative allylic hydroxylation and 1,3-functional group isomerization/aromatization followed by terminal oxidation to afford 3-acylindoles quantitatively with very high regioselectivity.

The synthesis of indole-3-carbinols (I3C) and their application to access unsymmetrical bis(3-indolyl)methanes (BIMs) bearing a quaternary sp-carbon.

In the present study, the novel synthesis of -indole-3-carbinols is reported through the DDQ-mediated oxidation of the allylic C-H bond/aromatization/hydroxylation at the indolyl carbon using water as the hydroxyl source. The reaction is highly efficient and high yielding and it works under mild reaction conditions. Furthermore, the synthetic value of such indole-based -carbinols is explored through their use as excellent electrophilic methylene surrogates to develop medicinally important unsymmetrical bis(3-indolyl)methanes containing an all carbon quaternary center.

DDQ/FeCl-mediated tandem oxidative carbon-carbon bond formation for the Synthesis of indole-fluorene hybrid molecules.

A series of diverse and complex hybrid structures of indole bearing fluorene were obtained in the presence of DDQ with high regioselectivity under mild conditions from biaryl tethered 3-(methylene)indoline in good to excellent yields. The strategy involves tandem allylic Csp-H oxidation and subsequent intramolecular carbon-carbon bond formation. The yield of the product was dramatically improved in the presence of additives such as FeCl and molecular sieves (4 Å).

Efficient two-step synthesis of structurally diverse indolo[2,3-b]quinoline derivatives.

A general and efficient synthesis of diverse tetracyclic indolo[2,3-b]quinoline derivatives was achieved through palladium-catalyzed domino carboannulation/cross-coupling and DDQ-mediated double cross-dehydrogenative C-N bond formation. This approach provides a straightforward, atom-economical and concise route to easily access a diverse range of tetracyclic indolo[2,3-b]quinolines and their analogues in excellent yields with good tolerance of functional groups.

Metal-Catalyzed Domino Synthesis of Benzophenanthridines and 6 H-Naphtho[2,3- c]-chromenes.

A new and efficient synthesis of tetracyclic phenanthridines and benzo[ c]chromenes has been described involving a metal-mediated two-step domino strategy. The first step involved efficient palladium-catalyzed domino carbopalladation/cross coupling, and the second step involved iron-catalyzed domino isomerization/cyclodehydration. The important features of this strategy include high yields, generality, wide substrate scope, and broad functional group tolerance.

Synthesis of Fused Dibenzofuran Derivatives via Palladium-Catalyzed Domino C-C Bond Formation and Iron-Catalyzed Cycloisomerization/Aromatization.

A range of tetracyclic dibenzofuran derivatives bearing a variety of functional groups was readily synthesized via a two-stage domino strategy starting from propargyl ethers of 2-halo phenol derivatives. The first stage in the strategy involves Pd(0)-catalyzed domino intramolecular carbopalladation/Suzuki coupling via 5-exo-dig cyclization onto the alkyne, leading to 3-methylene-2,3-dihydrobenzofuran derivatives. In the second stage of the domino strategy, an iron(III)-catalyzed cycloisomerization and aromatization reaction produces tetracyclic benzofuran derivatives.