Microwave‐Promoted, One‐Pot, Solvent‐Free Synthesis of 4‐Arylcoumarins from 2‐Hydroxybenzophenones

Abstract

4‐Arylcoumarins are synthesized in very good yields through solvent‐free microwave irradiation of 2‐hydroxybenzophenones and alkyl malonate in the presence of DBU. The one‐pot synthesis is carried out with Knoevenagel condensation, intramolecular lactonization, and decarboxylation reactions. The method can be applied to a broad scope of neoflavonoids.

Chlorinated Coumarins from the Polypore Mushroom Fomitopsis officinalis and Their Activity against Mycobacterium tuberculosis

“…Additional HMBC correlations of H-5 (δ 7.433) to C-8a (δ 7.433) and C-4 as well as H-7 to C-8a and C-5 confirmed the remaining coumarin skeleton. Compound 1 turned out to be a new naturally occurring chlorinated coumarin and was identified as the previously synthesized compound, 20 6-chloro-4-phenyl-2H-chromen-2-one. Since only sub-milligram quantities could be isolated, the compound was chemically synthesized in order to enable in depth chemical and biological evaluation.…”

Palladium(ii) oxide impregnated on magnetite as a catalyst for the synthesis of 4-arylcoumarins via a Heck-arylation/cyclization process

“…Particularly, 4-aryl derivatives constitute a subgroup of flavonoids that have received considerable attention, as they display important biological activities such as anti-HIV, antimalarial, antibacterial and cytotoxic properties. Classical synthetic approaches for the synthesis of 4-arylcoumarins are based on Knoevenagel condensation, 7 cross-coupling reactions, 8 C-H bond activation, 9 von Pechman condensation, 10 among others. 11 In many cases, the reactions were performed under harsh reaction conditions and high temperatures.…”

Microwaves in Heterocyclic Chemistry

“…Seijas and co-workers demonstrated the utility of microwave irradiation for the synthesis of 4-arylcoumarins in good yields [133]: the method was carried out with Knoevenagel condensation, intramolecular lactonization, and decarboxylation. A one-pot reaction is also possible from 2-hydroxybenzophenones and alkyl malonates in the presence of DBU (50 mol%) with a short reaction time (7 min (16.22) Owing to the potential interest in 2-(2-oxo-2H-chromen-2-yl)acetic acid for antineoplastic activity, Boháč and co-workers studied a protocol with microwave irradiation for a one-pot Perkin condensation with subsequent intramolecular lactonization [134].…”