Showing papers on "Benzopyrans published in 2016"

4H-1-Benzopyrans as Analytical Reagents - A Review

Abstract: 4H-1-benzopyrans and their derivatives have been used widely as analytical reagents for the spectrophotometric determination of several transition metal ions. The present article reviews the importance of 4H-1-benzopyrans as analytical or complexing or chelating agent and fundamental conditions of several methods used for analytical determination of metal ions spectrophotometrically.

Synthetic Anthocyanidins from Natural Benzopyrans

Abstract: A hydride abstraction strategy can be used to make anthocyanidins and isoflavylium salts from benzopyrans in good yields.

Chemistry of 3-carbonyl-2-methyl-4-oxo-4H-1-benzopyrans

Abstract: The review article gives a comprehensive survey of the synthesis and chemistry of the title benzopyrans covering the literature published during 1980 - August 2015.

Palladium-Catalyzed Double C-H Functionalization of 2-Aryl-1,3-dicarbonyl Compounds: A Facile Access to Alkenylated Benzopyrans.

Abstract: The present study reports the development of a palladium-catalyzed oxidative annulation/nucleophilic substitution sequence affording a library of alkenylated benzopyrans using 2-aryl-1,3-dicarbonyl compounds and allylic acetate. The process is compatible to a wide range of substrates with good functional group tolerance producing the desired heterocycles in moderate to good yields.

Synthesis of Furo[3,2-c]benzopyrans via an Intramolecular [4 + 2] Cycloaddition Reaction of o-Quinonemethides.

Abstract: An intramolecular [4 + 2] cycloaddition reaction of o-quinonemethides generated from salicylaldehydes and α-prenylated alcohols is described. In the presence of a catalytic amount of benzenesulfonic acid (BSA), the reaction proceeded smoothly in EtOH to afford furo[3,2-c]benzopyrans through a three-bond forming process in moderate to excellent yields with high diastereoselectivity. This reaction provides a simple and straightforward protocol to efficiently construct furo[3,2-c]benzopyran skeletons. A possible mechanism involving hemiacetal formation/hetero-Diels–Alder reaction is proposed to rationalize the observed results.

Asymmetric Roadmap to Diverse Polycyclic Benzopyrans via Phosphine-Catalyzed Enantioselective [4 + 2]-Annulation Reaction.

Abstract: The catalytic addition of the amino acid derived bifunctional N-acylaminophosphine to an α-substituted allene ester generated a zwitterionic dipole that engaged the vinylogous ester function of 3-cyano-chromones in a [4 + 2] annulation reaction to deliver tetrahydroxanthones embodying three consecutive chiral centers in high yields and with excellent enantioselectivities. The established asymmetric synthesis further paves the way to two different classes of complex, sp3-rich tetracyclic benzopyrans via efficient cascade reactions.

Novel Synthesis of Some 2-Aminochromene Derivatives Using Nano-Sized Zirconium Oxide as Catalyst.

Abstract: Chromenes (benzopyrans) which are components of many biologically active compounds1,2 are of increasing significance. They are used as anti-hypertensive,3 hypoglycemic,4 cardio-protective5, anti-tu...

Expedient Synthesis of Tricyclic Benzopyran-2-ones via N-Heterocyclic Carbene Catalyzed Annulation of Enals to α-Methylene Cycloalkanones.

Abstract: Tricyclic benzopyrans are medicinally important biologically active compounds. Synthesis of a series of tricyclic benzopyrans derivatives via N-Heterocyclic carbene (NHC) catalyzed annulation of enals to α-methylidenetetralones/chromanones is described. This reaction afforded the benzopyrans in high yield with aromatic as well as aliphatic enals.