Development of Novel Lewis Acid Catalysts for Selective Organic Reactions in Aqueous Media

Abstract

New types of Lewis acids as water-compatible catalysts have been developed. Various metal salts were found to work as Lewis acid catalysts in aqueous media, and catalytic asymmetric aldol reactions in such media have been attained. Furthermore, Lewis acid-surfactant combined catalysts, which can be used for reactions in water without using any organic cosolvents, have been also developed. These investigations will contribute to reducing the use of harmful organic solvents and to develop efficient catalytic systems which cannot be realized in conventional organic solvents.

Tandem Catalytic Depolymerization of Lignin by Water‐Tolerant Lewis Acids and Rhodium Complexes

“…(a) Lewis acid strength21 correlates with 4‐methylsyringol ( 9 a ) yields; (b) yields of 4‐methylphenols versus 4‐(1‐propenyl)phenols as a function of Sc(OTf) 3 loading, demonstrating the ability to tune product distribution.…”

Recent applications of rare-earth metal(III) triflates in cycloaddition and cyclization reactions

“…35,36 As was the case for DA reactions, rare-earth metal(III) triflates have also been successfully employed to promote heteroDiels-Alder reactions. [10][11][12][13][14][15] Below are notable examples of M(OTf) 3 -catalyzed HDA reactions published in the last five years.…”

“…73 Owing to their oxophilic character, water tolerability and pronounced Lewis acidic properties, lanthanide triflates were also successfully employed in a number of free radical processes. [10][11][12][13][14][15] Yang and co-workers have disclosed Yb(OTf) 3 -promoted 5-/6-exo-trig radical cyclization of α-phenylseleno amido esters 93 under UV irradiation to give rise to mono-and bicyclic nitogen heterocycles 94 (Scheme 26). 74 It was suggested that Yb(OTf) 3 played a two-fold role in promoting the radical process: increased electrophilicity of the α-radical intermediate via 1,3-dicarbonyl moiety chelation and accelerated PhSe group transfer.…”

“…[10][11][12][13][14][15] Therefore, the purpose of the present review is not to summarize all the efforts in the area comprehensively, but instead highlight a select number of important applications of rare-earth metal triflates in cyclization and cycloaddition reactions reported over the last five years, up to the first three quarters of 2013.…”

Selective chemical reactions in supercritical carbon dioxide, water, and ionic liquids

“…Nacci and co-workers reported (232) PdÁcarbene ligand catalyzed the carbonylation of aryl halides (114) in ILs (Scheme 36). Among the ILs used, tetrabutylammonium bromide (TBAB) was found to give better results.…”