One-step synthesis of furocoumarins via oxidative annulation of 4-hydroxycoumarins with DDQ

Versatile approach for the synthesis of furo-coumarin derivatives

Abstract:

Owing to useful physio-chemical properties of furo-coumarin derivatives, their synthetic and mechanistic investigation has been reported here. We have demonstrated a range of synthetic approach to access furan-fused coumarin derivatives. Many metal mediated, base and acid catalyzed approach have been revealed for the construction of thiscoumarin based fused heterocycles of biological importance. In addition to this, microwave assisted synthetic routes have been also revealed. The last and useful approach for the synthesis of these heterocycles includes use of purely solvent as a reaction media for synthesizing these interesting classes of heterocycles.

Coumarin-Annulated Ferrocenyl 1,3-Oxazine Derivatives Possessing In Vitro Antimalarial and Antitrypanosomal Potency

A tailored series of coumarin-based ferrocenyl 1,3-oxazine hybrid compounds was synthesized and investigated for potential antiparasitic activity, drawing inspiration from the established biological efficacy of the constituent chemical motifs. The structural identity of the synthesized compounds was confirmed by common spectroscopic techniques: NMR, HRMS and IR. Biological evaluation studies reveal that the compounds exhibit higher in vitro antiparasitic potency against the chemosensitive malarial strain (3D7 P. falciparum) over the investigated trypanosomiasis causal agent (T. b. brucei 427) with mostly single digit micromolar IC50 values. When read in tandem with the biological performance of previously reported structurally similar non-coumarin, phenyl derivatives (i.e., ferrocenyl 1,3-benzoxazines and α-aminocresols), structure-activity relationship analyses suggest that the presence of the coumarin nucleus is tolerated for biological activity though this may lead to reduced efficacy. Preliminary mechanistic studies with the most promising compound (11b) support hemozoin inhibition and DNA interaction as likely mechanistic modalities by which this class of compounds may act to produce plasmocidal and antitrypanosomal effects.

Palladium-Catalyzed Chemoselective Activation of sp3 vs sp2 C-H Bonds: Oxidative Coupling To Form Quaternary Centers

The oxidative activation of alkyl C-H bonds vs arene C-H bonds with Pd(OAc)₂ has been found to be generalizable to a number of nucleophilic substrates allowing the formation of a range of hindered quaternary centers. The substrates share a common mechanistic path wherein Pd(II) initiates an oxidative dimerization. The resultant dimer modifies the palladium catalyst to favor activation of alkyl C-H bonds in contrast to the trends typically observed via a concerted metalation deprotonation mechanism. Notably, insertion occurs at the terminus of the alkyl arene for hindered substrates. Two different oxidant systems were discovered that turn over the process. Parameters have been identified that predict, which substrates are productive in this reaction.

A new route to substituted furocoumarins via copper-catalyzed cyclization between 4-hydroxycoumarins and ketoximes

A new route to substituted furocoumarins via copper-catalyzed cyclization between 4-hydroxycoumarins and ketoximes was developed.

Copper powder-catalyzed chelation-assisted cascade reaction of o-chloroarylacetic acids with amines under solvent- and ligand-free conditions: synthesis of oxindoles

Copper powder-catalyzed sequential C–Cl amination/intramolecular N-acylation under solvent- and ligand-free conditions is developed to access oxindoles.