Cesium and Aluminum Salts of Dodecatungstophosphoric Acid as Eco-Friendly and Efficient Heterogeneous Catalysts in Organic Synthesis: Some Recent Advances

Abstract

In this review we have paid attention to cesium and aluminum salts of dodecatungstophosphoric acid as ecofriendly and efficient heterogeneous catalysts. The structural effect and also catalytic properties of exchanging Cs + with protons in dodecatungstophosphoric acid is discussed. Using cesium and aluminum salts of dodecatungstophosphoric acid as efficient catalysts for Friedel-Crafts reactions such as acylation and alkylation of aromatic compounds, Fries, Claisen and pinacol rearrangements, esterification, amidation, ether formation, protection of thiols, alcohols and amines, conversion of aldehydes to their acylals, ring opening of epoxides, selective protection of one hydroxy group in diols, preparation of -hydroxythioethers and regioselective bromination of aromatic compounds are discussed.

Toward a rational control of solid acid catalysis for green synthesis and biomass conversion

“…56 It is established that H 3 PW 12 O 40 , a Keggin type of heteropolyacid, has higher Brønsted acidity than triflic acid, 58 and acts as an efficient Brønsted acid catalyst. [22][23][24][59][60][61][62][63][64][65] Knowing the fact that metal salts of heteropolyacids [66][67][68][69] potentially show Lewis acidity 64 originated from metal cation as electron pair acceptors, we hypothesized that metal salts of heteropolyacids will act analogously to metal triflates. Very few successful examples are reported on the use of them as efficient acid catalysts for organic reactions.…”

“…Very few successful examples are reported on the use of them as efficient acid catalysts for organic reactions. 26,27,69 Friedel-Crafts alkylation and acylation of aromatic compounds are important processes in both petroleum and chemical industries. 70 The conventional method, using alkyl halides as alkylating agents and acid chlorides or acid anhydrides as acylation agents with a stoichiometric amount of acid promoter (AlCl 3 or H 2 SO 4 ), suffers from severe corrosion, waste, and safety problems.…”

“…For the Friedel-Crafts acylation of aromatics by carboxylic acids, as the greenest methods to prepare aromatic ketones, various catalytic methods have been attempted. 62,69,[76][77][78][79][80][81][82][83][84] Okumura found that HPNbW-WO 3 -Nb 2 O 5 catalyst was effective for the Friedel-Crafts acylation of anisole with carboxylic acids. 77 With this catalyst, a flow-type reaction was possible over a period of 7 days.…”

“…These values are more than two orders of magnitude larger than those reported for this reaction: TON ¼ 5.8 and TOF ¼ 0.9 h À1 for Eu(NTf 2 ) 3 , 83 TON ¼ 6.4 and TOF ¼ 0.8 h À1 for AlPW 12 O 40 . 69 Acylation of toluene with a variety of straight chain C 6 -C 19 carboxylic acids and benzoic acid gave the corresponding acylated products in good to excellent yields (87-94%). The rate of acylation increases with electronegativity of cation (Fig.…”

Atomically Dispersed Rhodium on Self-Assembled Phosphotungstic Acid: Structural Features and Catalytic CO Oxidation Properties

“…Currently, K + , Cs + , and NH 4 + are the most utilized inorganic cations to form the skeleton of HPA salts with a specific surface of around 60 to 200 m 2 /g (determined by N 2 adsorption), which is comparable to many common supports. , Among transitional metals, Ag, Pd, and Pt incorporated within the crystalline structures have been extensively examined in a number of catalytic reactions, , including alkane isomerization and alkene oxidation as well as the esterification reactions . In many cases, researchers treat the precatalysts under severe conditions to obtain metal NPs or NCs as the active sites. , Rh has also been examined in self-assembled HPA porous materials, but only a few studies were performed, and the application was limited. ,, For instance, carbonization of dimethyl ether in the presence of CO has been illustrated over Rh/Cs 2 PW 12 O 40 , but the structure of the catalysts was not thoroughly characterized .…”