Synthesis and reactivity of styrylchromones

Abstract

2-Styrylchromones, although scarce in nature, constitute a group of oxygen heterocyclic compounds which have shown significant biological activities. Their transformation and the transformation of their 3-isoanalogues into other biologically active compounds have been exploited. This short review describes the most recent work on the synthesis, biological evaluation and transformation of 2-and 3-styrylchromones.

Synthesis of (E)-2-Styrylchromones and Flavones by Base-Catalyzed Cyclodehydration of the Appropriate β-Diketones Using Water as Solvent

“…The typical established methods for the cyclodehydration reaction of 5-aryl-1-(2-hydroxyphenyl)pent-4-ene-1,3-diones 4 involve the use of strong acidic conditions, p -toluenesulfonic acid, or a catalytic amount of iodine in DMSO at 90–100 °C [16,17,18,25]. In order to establish a more environmental friendly procedure for this cyclodehydration reaction commonly used in our research group, we performed the base-catalyzed (potassium carbonate) cyclodehydration reaction of 4a in water.…”

“…Flavones ( I ), the most prominent group of naturally occurring chromones, are present in a wide variety of plants [1] and are well-known by their broad range of biological properties, such as antibacterial, antifungal [2,3], antiviral [4], antiinflammatory [5], antioxidant [6], antiallergic [7], hepatoprotective [8], antithrombotic and antitumoral [9,10] activities (Figure 1). In contrast to flavones, there are only nine natural ( E )-2-styrylchromones II – X [11,12,13,14,15], a group of oxygen heterocyclic compounds that although being scarce in Nature have shown significant biological activities [16,17,18] (Figure 1). 2-Styrylchromones have potential therapeutic applications in the treatment of cancer [19], allergies [20], viral infections [21], gout [22] and oxidative stress related damage [23].…”

“…The most common strategies for the synthesis of ( E )-2-styrylchromones are the aldol condensation of 2′-hydroxyacetophenone derivatives with cinnamaldehydes, followed by cyclodehydrogenation of the formed 2′-hydroxycinnamylideneacetophenones, and the Baker-Venkataraman method [16,17,18,25]. This second strategy involves the O -acylation of 2′-hydroxyacetophenone ( 1 , Scheme 1, step i) followed by base-catalyzed rearrangement of the formed esters 3 to give 5-aryl-1-(2-hydroxyphenyl)pent-4-ene-1,3-diones 4 (which exist in equilibrium with their enolic form; Scheme 1, step ii).…”

“…This rearrangement can be performed in high yield under solvent-free conditions, using grinding techniques [26]. The last step of this method consists in the cyclodehydration of compounds 4 into ( E )-2-styrylchromones 5 , using strong acidic conditions, p -toluenesulfonic acid or a catalytic amount of iodine in DMSO at 90–100 °C (Scheme 1, step iii) [16,17,18,25].…”

Synthesis and Reactivity of Electron-Deficient 3-Vinylchromones

“…Meanwhile, in recent years, interest in these readily available representatives of the family of 3-substituted chromones has been growing, and their chemistry is developing intensively, deserving a separate discussion. This review systematizes the data on 3vinylchromones having one or two electron-withdrawing groups at the 2'-position (with the exception of 3styrylchromones 10 ), published mainly over the past 15 years, as well as some earlier works necessary to create a coherent and complete picture.…”