Palladium-catalyzed [5+2] oxidative annulation of N-Arylhydrazones with alkynes through C H activation to synthesize Benzo[d][1,2]diazepines

Palladium-catalyzed C-C bond cleavage of N-cyclopropyl acylhydrazones

Despite their utility as directing groups, the C-C bond cleavage of cyclopropanes utilizing hydrazones has not been explored. Herein, Pd-catalyzed C-C bond cleavage reaction of N-cyclopropyl acylhydrazones, followed by cycloisomerization to yield pyrazoles, has been developed. The protocol enables the synthesis of various α-pyrazole carbonyl compounds, which have a potential of biological activity. Control experiments and DFT calculations suggest that β-carbon elimination of a stable 6-membered chelate palladium complex occurs, generating a conjugated azine as a reaction intermediate for the following cycloisomerization.

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

A straightforward synthetic protocol for the efficient construction of diazepine-containing spiroindolines has been developed and proceeds through a by base-promoted annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates. The reaction mechanism of this formal [4 + 3] annulation includes the in situ generated allylic ylide, nucleophilic substitution, Michael additon, and elimination processes. Additionally, the similar reaction with α-halogenated N-tosylhydrazones also afforded N-tosyl-substituted spiro[indoline-3,5'-[1,2]diazepine] in satisfactory yields. This protocol provides a convenient approach for the assembly of diverse highly functionalized spiro[indoline-3,5'-[1,2]diazepines] and also features a broad substrate scope, simple reaction conditions, and high molecular convergence.

Construction of aziridine, azetidine, indole and quinoline-like heterocycles via Pd-mediated C-H activation/annulation strategies

N-Heterocycles can be found in natural products and drug molecules and are indispensable components in the area of organic synthesis, medicinal chemistry and materials science. The construction of these N-containing heterocycles by traditional methods usually requires the preparation of reactive intermediates. In the past decades, with the rapid growth of transition metal catalysed coupling reactions, syntheses of heterocycles from precursors with inert chemical bonds have become a challenge. More recently, in the field of transition metal associated C-H direct functionalization, efficient methods have been developed for the syntheses of N-heterocyclic compounds such as aziridines, azetidines, indoles and quinolines under the click type of reaction mode. In this review, representative synthetic methodologies developed in the recent 10 years for the preparation of this small class of N-heterocycles via the Pd-catalysed C-H activation and C-N bond formation pathway are discussed. We hope this article will provide new insights from the strategies highlighted into future molecular design, synthesis and applications in medical and materials sciences.

Synthesis of α-Branched Amines by Three- and Four-Component C-H Functionalization Employing a Readily Diversifiable Hydrazone Directing Group

Efficient syntheses of α-branched amines by three- and four-component C-H functionalization employing a diversifiable hydrazone directing group have been developed. The hydrazone in the α-branched amine products has been readily converted to multiple desirable functionalities such as a nitrile, a carboxylic acid, alkenes, and heterocycles using diverse heterolytic chemistry and homolytic transition metal- or photoredox-catalyzed processes. This study represents the first example of a four-component C-H functionalization reaction.

Palladium-Catalyzed Benzodiazepines Synthesis

This review is focused on palladium-catalyzed reactions as efficient strategies aimed at the synthesis of different classes of benzodiazepines. Several reaction typologies are reported including hydroamination, amination, C–H arylation, N-arylation, and the Buchwald–Hartwig reaction, depending on the different substrates identified as halogenated starting materials (activated substrates) or unactivated unsaturated systems, which then exploit Pd(0)- or Pd(II)-catalytic species. In particular, the use of the domino reactions, as intra- or intermolecular processes, are reported as an efficient and eco-compatible tool to obtain differently functionalized benzodiazepines. Different domino reaction typologies are the carboamination, aminoarylation, aminoacethoxylation, aminohalogenation, and aminoazidation.

Synthesis of pyrazolone fused benzodiazepines via Rh(iii)-catalyzed [4 + 3] annulation of 1-phenylpyrazolidinones with propargyl alcohols

An efficient synthesis of pyrazolone fused benzodiazepines through an unprecedented regioselective [4 + 3] annulation of 1-phenylpyrazolidinones with propargyl alcohols via Rh(iii)-catalyzed redox-neutral C–H/N–H/C–O bond activation is presented.

Synthesis, in vitro COX-1/COX-2 inhibition testing and molecular docking study of novel 1,4-benzoxazine derivatives

The present work deals with an efficient and straightforward synthesis, biological activity and molecular docking study of novel 1,4-benzoxazine derivatives.