Dramatic Enhancement of Catalytic Activity in an Ionic Liquid: Highly Practical Friedel–Crafts Alkenylation of Arenes with Alkynes Catalyzed by Metal Triflates

Innovative Catalytic Protocols for the Ring‐Closing Friedel–Crafts‐Type Alkylation and Alkenylation of Arenes

“…In fact, "... one major drawback from the direct FC alkenlylation of arenes is the alkyne polymerization ...". [20] Mechanistically, although different rationales have been proposed that depend both on metal salts and reaction conditions, the interaction between the C-C triple bond and the catalyst is considered to be the key step during the nu-cleophilic attack on the tethered alkyne moiety to give predominantly the 6-endo-dig product (Figure 2). In particular, the high electron affinity of electrophilic late transition metals for π-systems and their excellent tolerance toward many hard functional groups suggest transition metal salts to be potentially effective catalysts for the cycloisomerization of alkynes.…”

“…In particular, Hashmi has reported the synthesis of substituted arenes 19 starting from 18 under mild conditions (AuCl 3 , 2 %, CH 3 CN), [30a] with the reaction mechanism being an intramolecular [4 + 2] cycloaddition between the furan and the alkyne. Therefore, the gold-catalyzed reaction was employed in the multi-step synthesis of jungianol (20), allowing its synthesis to be shortened considerably (Scheme 7).…”

A high hydroarylation activity of K2PtCl4/AgOTf catalyst in the reaction of propiolic acid with unactivated and activated arenes

“…Several transition metal compounds catalyze hydroarylation of alkynes in a manner of C-H bond activation or electrophilic substitution [3][4][5][6][7][8][9][10][11][12][13]. Transition metal catalyzed-addition reactions of arenes having directing groups such as carbonyl, imino and nitrile groups via chelation-assisted C-H bond functionalization have been extensively studied [1h,i].…”

Lanthanides and Actinides in Ionic Liquids

“…191 The reaction between benzene and 1-phenyl- Different rare-earth triflates were tested, and besides scandium(III) triflate, good catalytic activity was found for yttrium(III), ytterbium(III), and lutetium(III) triflates. It is remarkable that a higher catalytic activity was observed for yttrium(III) triflate than for scandium(III) triflate, although holmium(III) and erbium(III) triflate are much less active.…”