Synthetic approach to flavanones and flavones via ligand-free palladium(ii)-catalyzed conjugate addition of arylboronic acids to chromones

Abstract

The remarkable catalytic effects of Fe(OTf)(3) in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO(2) to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.

Efficient Synthesis of Frutinone A and Its Derivatives through Palladium‐Catalyzed CH Activation/Carbonylation

“…Having determined the optimized CH activation/carbonylation conditions, we next turned our attention to the efficient and step‐economical synthetic route to frutinone A. Recently, our group reported a practical method for the palladium‐catalyzed 1,4‐addition of arylboronic acids to chromones in the presence of a catalytic amount of Fe(OTf) 2 , which thereby gave a variety of flavone analogues as major products under mild conditions 7. This protocol was subjected to a straightforward synthetic route to frutinone A and its derivatives, as outlined in Scheme .…”

“…Recently, our group reported ap ractical methodf or the palladium-catalyzed 1,4-addition of arylboronic acids to chromones in the presence of ac atalytic amounto fF e(OTf) 2 ,w hich thereby gave av ariety of flavone analogues as major products under mild conditions. [7] This protocol was subjected to as traightforward synthetic route to frutinone Aand its derivatives, as outlined in Scheme 2. Thus, required 2-phenol chromone 1a was conveniently prepared by palladium-catalyzed 1,4-addition of methoxyphenylboronic acid 4 to chromone 3,f ollowed by the demethylationo f5with BBr 3 .N ext, ap alladium-catalyzed CÀHa ctivation/carbonylation reactionw as applieda nd frutinone Aw as obtained by starting from commercially available chromone 3 in at otal yield of 44 %o ver three steps (see Scheme 3).…”

In VitroEnzyme Inhibition Potentials and Antioxidant Activity of Synthetic Flavone Derivatives

“…The final products (mixture of flavone and chalcone) were subjected to column chromatography using n-hexane: ethyl acetate (9 : 1) to purify flavones derivatives ( Figure 1) [17]. [18,19]. After 30 minutes, the absorbance was measured at 517 nm.…”

Rhodium(III)-catalyzed one-pot synthesis of flavonoids from salicylaldehydes and sulfoxonium ylides

“…16 Therefore, the development of efficient methods to synthesize flavonoid scaffolds remains a topic of interest. [17][18][19][20][21][22][23][24] In recent years, transition metal catalyzed C-C bond and C-hetero bond formation are effective methods for the synthesis of flavonoids. 25,26 Baruah et al 27 developed Ru(II)-catalyzed C-H activation and annulations of salicylaldehydes and alkynes to afford flavonoids (Scheme 1(a)).…”