Alcohol Mediated Synthesis of 4-Oxo-2-aryl-4H-chromene-3-carboxylate Derivatives from 4-Hydroxycoumarins

Abstract

The unusual alcohol mediated formation of 4-oxo-2-aryl-4H-chromene-3-carboxylate (flavone-3-carboxylate) derivatives from 4-hydroxycoumarins and β-nitroalkenes in an alcoholic medium is described. The transformation occurs via the in situ formation of a Michael adduct, followed by the alkoxide ion mediated rearrangement of the intermediate. The effect of the different alcohol and nonalcohol media on the reaction was investigated.

Recyclable and reusable PdCl2(PPh3)2/PEG-2000/H2O system for the carbonylative Sonogashira coupling reaction of aryl iodides with alkynes

“…Flavones are an important class of naturally occurring products, [47][48][49] and many methods for their preparations have been published. [50][51][52][53][54][55][56][57][58] Recently, the palladium-catalyzed carbonylation of o-iodophenol derivatives with terminal alkynes to prepare flavones has attracted considerable interest. [59][60][61][62][63][64][65] We also investigated the feasibility of preparing flavones by the sequential carbonylative coupling of o-iodophenol with terminal alkynes to form α,β-unsaturated ketones, followed by an intramolecular cyclization to give flavones in a one-pot operation using PdCl 2 (PPh 3 ) 2 /PEG-2000/H 2 O as To check the reusability of PEG-2000 and the catalyst, the carbonylative coupling reaction of 4-iodoanisole with phenylacetylene was examined in the presence of 5 mol% PdCl 2 (PPh 3 ) 2 .…”

Recent advances in the synthesis of 4H-chromen-4-ones (2012 − 2021)

“…The synthesis of 2-aryl-4-oxo-4H-chromen-3-carboxylates has been accomplished through three-component reaction of 4-hydroxy-2Hchromen-2-ones with β-nitroalkenes and different alcohols in the presence of triethylamine (Scheme 80) 424 or DMAP, 425 at 70-80 °C. Further derivatives were formed via multicomponent reaction of 4-hydroxy-2H-chromen-2-one with benzaldehydes, nitromethane and methanol in the presence of triethylamine.…”

“…Further derivatives were formed via multicomponent reaction of 4-hydroxy-2H-chromen-2-one with benzaldehydes, nitromethane and methanol in the presence of triethylamine. 424 Reacting 4-hydroxy-2H-chromen-2-one with β-nitroalkenes and different amines in the presence of DMAP at 70-80 °C prompted few 2-aryl-4-oxo-4H-chromen-3-carboxamides, in 65-69% yield. 425…”

A Review on the Synthetic Methodologies of Chromones

“…A mild ICl-induced cyclization of heteroatom-substituted alkynones provides a simple, highly efficient approach to various 3-iodochromones, iodothiochromenones, iodoquinolinones, and analogs in good to excellent yields. Subsequent palladium-catalyzed transformations afford a rapid increase in molecular complexity [47].…”