Silica sulfuric acid: A simple, efficient, and reusable heterogeneous catalyst for the one-pot synthesis of aryl-14H-dibenzo[a,j]xanthenes under conventional heating and solvent-free conditions

Abstract

A novel approach towards the one-pot synthesis of aryl-14H-dibenzo [a,j]xanthenes is described from a known reaction between substituted aldehydes and β-naphthol in the presence of heterogeneous catalyst silica sulfuric acid under conventional heating as well as solvent-free conditions to afford good to excellent yields. The catalyst is reusable; it can be used several times without any decrease in the product yield.Considerable interest has been focused on the synthesis of xanthenes; in particular, benzoxanthenes have attracted much attention in recent years because of their wide range of biological and pharmacological applications, such as antiviral [1], attention [2], and anti-inflammatory [3] properties. They also exhibited efficacy in photodynamic therapy [4,5] and are antagonists against the paralyzing action of zoxazolamine [6,7]. In addition, these compounds have also been employed as dyes [8,9], in laser technologies [10,11], and in fluorescent materials for visualization of biomolecules [12].The most commonly employed methods are available for the synthesis of xanthenes, and the synthesis of benzoxanthenes involves cycloacylation of carbamates [13], cyclodehydration [14][15][16][17][18], cyclocondensation between 2-hydroxy aldehydes and 2-tetralone [19], trapping of benzynes by phenols [20,21], intramolecular coupling reaction of benzaldehyde and acetophenones [22], aldehydes and β-naphthols by dehydration [15,[23][24][25], and β-naphthol with: i) formamide [26], ii) carbon monoxide [27], aldehyde acetals, and 2-naphthol-1-methanol [28]. Although some of these methods are useful, the majority of the above methods suffer from at least one of the following disadvantages: low yield, prolonged reaction time, use of toxic organic solvents, excess of reagents and catalysts, high cost, and susceptibility to moisture. There is still a need for an efficient economical and excellent yielding catalyst that can work under mild conditions and shorter reaction time and avoid the use of toxic reagents and solvents. __________________________________________________________________________________________

Efficient one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride

“…The reaction between 2-naphthol (IV ) and ben- (Hunnur et al, 2008) a) Yield of isolated products; b) all products are known and their melting points were compared with values already reported. zaldehyde (Va) was used as a reaction model in order to develop a protocol for the optimisation of the reaction conditions.…”

Fe3O4@SiO2–imid–PMAnmagnetic porous nanospheres as recyclable catalysts for the one-pot synthesis of 14-aryl- or alkyl-14H-dibenzo[a,j]xanthenes and 1,8-dioxooctahydroxanthene derivatives under various conditions

“…26 One of these methods is the condensation reaction of aldehydes with b-naphthol for the synthesis of 14-aryl or alkyl-14Hdibenzo[a, j]xanthenes, and many catalysts such as H 5 PW 10 V 2 O 40 , 27 KAl(SO 4 ) 2 Á12H 2 O (alum), 28 nano-TiO 2 . 29 Succinimide-N-sulfonic acid, 30 MeSO 3 H, 31 iodine, 32 silica sulfuric acid, 33 boric acid, 34 cyanuric chloride 35 and [Et 3 N-SO 3 H]Cl 36 have been used for the synthesis of 14-aryl or alkyl-14H-dibenzo[a, j ]xanthene derivatives.…”

Microwave-assisted green synthesis of dibenzo[a,j]xanthenes using p-dodecylbenzenesulfonic acid as an efficient Bronsted acid catalyst under solvent-free conditions

“…However, the synthesis of dibenzoxanthenes via one-pot condensation of b-naphthol with aldehydes has been widely studied. This reaction has been catalyzed by a wide range of catalysts including pTSA [16], P 2 O 5 /Al 2 O 3 [17], ruthenium chloride hydrate [18], ionic liquids [19], methanesulfonic acid [20], LiBr [21], silica sulphuric acid [22], K 5 CoW 12 O 40 .3H 2 O [23], HClO 4 [24], sulfamic acid [25], alum [26], In(OTf) 3 [27], or Sc[N(SO 2 C 8 F 17 ) 2 ] 3 [28] etc. Though each of above mentioned methods has demonstrated its own merits, several of these protocols suffer from one or more drawbacks such as prolonged reaction times, use of hazardous solvents, necessity of excess reagents or catalysts, harsh reaction conditions or low yields of the desired products.…”