Catalytic application of two novel sandwich-type polyoxometalates in synthesis of 14-substituted-14H-dibenzo[a, j]xanthenes

Abstract

Two sandwich-type polyoxometalates K 12 [As 2 W 18 Cu 3 O 68 ]•30H 2 O and K 12 [As 2 W 18 U 3 O 74 ]•21H 2 O were found to be as novel efficient catalysts for one-pot synthesis of various 14-aryl or alkyl-14Hdibenzo[a, j]xanthenes. Three-component condensation reactions of β-naphthol with aromatic or aliphatic aldehydes in the presence of these catalysts were investigated. These reactions were studied under different conditions such as solvent-free media using both conventional heating and microwave irradiation and also several solvents. Results showed that the optimum reaction time and the yield were obtained when reactions were carried out under solvent-free conditions. Furthermore, the catalysts could be recovered conveniently and reused efficiently.

One-Pot Synthesis of Novel Dibenzoxanthenes, Diarylbutanes, and Calix[4]resorcinarenes via Consecutive Pyrrolidine Ring-Closure/Ring-Opening Reactions

“…Taking into consideration previously published data [30,40], we proposed the mechanism of this reaction depicted in Scheme 6. e first stage of the reaction is a protonation of ethoxy group and elimination of ethanol molecule. e oxonium cation A thus formed may further react with phenol molecule, leading to the 2-arylpyrrolidine derivative B as previously described [24].…”

Recent Advances of Anderson-Type Polyoxometalates as Catalysts Largely for Oxidative Transformations of Organic Molecules

“…The applications in organic reaction are still the confronting great challenge. With the structural development of Anderson-type POMs, a mounting number of researchers began to study the modification of POMs which controlled the application in the catalytic field [14][15][16][17][18][19]. These studies illustrate that Anderson-type POMs not only possess acid-based properties, but also excellent redox performance for the contributor that is present in central atoms.…”