Three-Component Synthesis of a Library of m-Terphenyl Derivatives with Embedded β-Aminoester Moieties

The three-component reaction between alkyl- or arylamines, β-ketoesters and chalcones in refluxing ethanol containing a catalytic amount of Ce(IV) ammonium nitrate allowed the construction of a large library of highly substituted dihydro- m-terphenyl derivatives containing β-alkylamino- or β-arylamino ester moieties. This process generates three new bonds and one ring and proceeds in high atom economy, having two molecules of water as the only side product. Another domino process, in which the original MCR was telescoped with a subsequent aza Michael/retro-aza Michael sequence, allowed the one-pot preparation of a library of compounds with a N-unsubstituted β-aminoester fragment. Finally, to extend the structural diversity of these libraries, we also examined the aromatization of the central ring of our compounds in the presence of dichlorodicyanoquinone. This reaction sequence did not affect the integrity of a stereogenic center belonging to the amino component.

Amine-Triggered Highly Facile Oxidative Benzannulation Reaction for the Synthesis of Anthranilates under Solvent-Free Calcium(II) Catalysis

An amine-triggered facile synthetic approach of anthranilates has been described through benzannulation of readily available chemicals under one-pot solvent-free conditions using Ca(OTf)₂ as the sustainable catalyst. In this regioselective approach, we described a reasonably longer cascade, which proceeds through β-enamino ester formation/Michael addition/intramolecular aldol reaction/elimination/aromatization/oxidative debenzylation/lactonization with a broad substrate scope and high yields. The isolation of intermediates authenticated the mechanism, and the synthetic utility of the products was also demonstrated.