A Mild, Highly Efficient Addition of Alkynes to Aldehydes Catalyzed by Titanium Dioxide‐Supported Silver Nanoparticles

Abstract

Titanium dioxide-supported silver nanoparticles were utilized as a highly efficient catalyst for the addition of terminal alkynes to aldehydes to prepare propargylic alcohols with the promotion by triphenylphosphine. Both a significant support effect and a ligand effect were observed in the catalytic reaction. With this protocol, various propargylic alcohol derivatives were synthesized from aldehydes and terminal alkynes in good to excellent yields. Furthermore, the catalyst could be recovered and reused effectively without obvious reduction in catalytic activity.Keywords: ligand promotion; propargylic alcohols; silver nanoparticles; support effects Propargylic alcohols are of considerable interest in organic synthesis because they are useful precursors for the synthesis of various important core structures in organic chemistry, such as indenes, furans, pyrroles, thiophene, triazoles, a,b-unsaturated aldehydes, and ketones, et al.[1] Recently, several different methods for preparing propargylic alcohols have been reported. Compared with the classical method using metal acetylides, an alternative and more atom-economical approach involves the catalytic addition of terminal alkynes to aldehydes. Recently, Carreira and co-workers developed a ZnA C H T U N G T R E N N U N G (OTf) 2 -catalyzed addition of alkynes to aliphatic aldehydes.[2] Shibasaki et al. reported a catalytic alkynylation of aldehydes and ketones with InBr 3 or InA C H T U N G T R E N N U N G (OTf) 3 as catalyst.[3] Li and his coworkers reported a RuCl 3 /InCl 3 -catalyzed alkynylation of aldehydes in water, [4] and then, a silver(I) phosphine complex-catalyzed reaction was also reported. [5] Recently, much attention has been attracted to the use of nanoparticles as catalysts in organic reactions, [6] because their intriguing properties are different from those of their corresponding bulk materials. Metal nanoparticles have a characteristic high surface area that translates into more active sites per unit area, and can maximize the reaction rates and minimize consumption of the catalyst. Because of their easy preparation and relative stabilities in air, the nanoparticles of coinage metals, such as copper, silver and gold, were widely reported, and there are many excellent examples on their applications as catalysts in organic reactions. In comparison with many examples using copper [7] or gold nanoparticles [8] as catalysts, there are only a few reports on the use of silver nanoparticles (Ag NPs) as catalyst, and in most cases, Ag NPs worked as dehydrogenation catalysts.[9] Few reports were concerned with the construction of carbon-carbon bonds or carbon-hetero bonds.[10] Very recently, we observed that carbon-supported Ag NPs could be used as catalyst for a highly efficient annulation of 2-(1-hydroxy-3-arylprop-2-ynyl)phenols to prepare the key intermediate of aurones with the promotion of phosphine ligands, which was also the first example about the ligand effect on Ag NPs.[11]Herein, we wish to report a highly efficient addition of alky...

Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals

“…Although nanosilver-catalyzed A 3 -coupling of aldehydes, alkynes, and amines has been determined in 2010, the first example of 1,2addition of alkynes to aldehydes that catalyzed by silver nanoparticles was only reported in 2012. 95 In this work, Yao et al found the titanium oxide-supported silver nanoparticles could be utilized as an efficient catalyst for the direct addition of terminal alkynes to aromatic aldehydes ( More importantly, on the basis of the nanoAg@TiO 2 @PMHSIPNcatalyzed alkynylation of trifluoromethyl ketones, we developed a new concept that high-reactive substrate as a "reactive tractor" to pull transformation of low-reactive substrates, called as springboard chemistry or HDL catalysis, in which we found trifluoromethyl ketone could be used as a high-reactive additive for the activation of nanosilver-catalyzed alkynylation of aldehydes dramatically. 96 The nanosilver-catalyzed alkynylation of aromatic aldehydes proceeded in good to high yields under optimized reaction conditions (Scheme 37, up to 99% yield).…”

“…The effect of particle size of nanosilver on catalytic addition of alkyne 86a to aromatic aldehyde 85a 95. …”

N‐Heterocyclic Carbene‐Protected Ag Nanoparticles Immobilized on Polyacrylonitrile Fiber as Efficient Catalysts for a Three‐Component Coupling Reaction

“…Later, copper salts, In 2 O 3 NPs, Fe III , cobalt, Ag I , and AuNPs were also employed as catalysts in the AHA coupling reaction. In addition, the deprotonation of C sp −H bonds by AgNPs has been reported . However, the development of a new highly efficient and environmentally friendly AgNP catalytic system for the AHA coupling reaction is still desirable.…”

“…In addition, the deprotonation of C sp ÀHb onds by AgNPsh as been reported. [19,47] However, the development of anew highly efficient and environmentally friendly AgNP catalytic system for the AHA coupling reactioni s still desirable.…”

Heterocyclic thiolates and phosphine ligands in copper‐catalyzed synthesis of propargylamines in water

“…[ 3 ] Silver chloride salt or silver nanoparticles in combination with tertiary phosphines is a well‐established method to efficiently catalyze A3 coupling reactions in water. [ 4–22 ] Progress in the synthesis of highly ordered mesoporous organic polymers has allowed their surface decoration with transitions metal ions via grafting techniques. [ 23,24 ] Transition metal ion‐grafted mesoporous organic polymers were utilized by various groups as efficient catalysts in the multicomponent coupling reactions.…”