Pd/C: An efficient and reusable catalyst for the synthesis of flavones via carbonylation of aryl halides

Abstract

This work describes an efficient and mild approach for the synthesis of flavones via catalytic carbonylation of aryl halides with 2‐hydroxyacetophenone using the commercial Pd/C as an efficient, heterogeneous and recyclable catalyst. Under balloon pressure of CO, 0.6 mol% Pd/C is sufficient for moderate yields of flavones for the carbonylation of aryl iodides under phosphine‐free conditions and aryl bromides in the presence of phosphine ligand. The catalyst is easily separable and shows significant recyclability. Moreover, the reaction mechanism was discussed, and a possible mechanism that contains two different cyclisation pathways was proposed.

Synergistic or antagonistic antioxidant combinations – a case study exploring flavonoid-nitroxide hybrids

“…[36][37][38] There are also recent reports of one-pot syntheses of flavones using modified Baker-Venkataraman reactions. [39][40][41][42][43][44][45][46][47][48] This methodology enables access to the two flavonoid classes of interest, flavone (2, 4) and 3-benzoyl flavone (3,5), in a single reaction. 43,44 Both of these approaches were investigated in the synthesis of the target nitroxide-flavonoid hybrid antioxidants (6-9) (Scheme 1).…”

Recyclable Palladium-Catalyzed Carbonylative Cyclization of Aryl Iodides and 2-Hydroxyacetophenones towards Flavones

“…Additionally, Lei et al described a Pd/Ccatalyzed carbonylative coupling of aryl halides with 2-hydroxyacetophenones towards flavones with moderate yields, however, the activity of the Pd/C catalyst also decreased gradually during recycling, and only a limited substrate scope was explored. 21 Therefore, the development of novel heterogeneous palladium catalytic systems with both high activity and excellent recyclability for the carbonylative assembly of flavones is highly desirable.…”

“…Additionally, Lei et al described a Pd/Ccatalyzed carbonylative coupling of aryl halides with 2-hydroxyacetophenones towards flavones with moderate yields, however, the activity of the Pd/C catalyst also decreased gradually during recycling, and only a limited substrate scope was explored. 21 Therefore, the development of novel heterogeneous palladium catalytic systems with both high activity and excellent recyclability for the carbonylative assembly of flavones is highly desirable. Mesoporous silica (MCM-41) has proven to be an ideal support for anchoring homogeneous metal catalysts owing to its specific properties such as ultrahigh surface area, large and defined pore size, large pore volume, and excellent thermal stability.…”

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

“…178 A similar strategy described by Lei et al started from the reaction of 2 0 -hydroxyacetophenone with aryl halides involving palladium on carbon as an efficient and recyclable catalyst giving several 2-aryl-4H-chromen-4-ones in good yields (Scheme 20). 179 Scheme 19 Scheme 20…”