Electrophilic alkenylation of aromatics with phenylacetylene over zeolite HSZ-360

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

“…The catalytic activities of other metal triflates were also investigated, for example (yields are given in parentheses), Ag(OTf) (4 %), Cu(OTf) 2 (27 %), Mg(OTf) 2 (21 %), Zn(OTf) 2 (2 %), Sn(OTf) 2 (69 %), La(OTf) 3 (62 %), Pr(OTf) 3 (19 %), Nd(OTf) 3 (37 %), Sm(OTf) 3 (15 %), Eu(OTf) 3 (16 %), Gd(OTf) 3 (23 %), Tb(OTf) 3 (34 %), Dy(OTf) 3 (28 %), Ho(OTf) 3 (30 %), Er(OTf) 3 (40 %), and Tm(OTf) 3 (22 %). However, their catalytic activities were much lower than those of Sc(OTf) 3 , In(OTf) 3 , Hf(OTf) 4 , Y(OTf) 3 , Yb(OTf) 3 , and Lu(OTf) 3 .…”

“…Finally, our protocol has been further extended to intramolecular Friedel-Crafts alkenylations. The intramolecular reaction of aryl phenyl propiolates catalyzed by Hf(OTf) 4 (10 mol %) in a mixture of [bmim][SbF 6 ] and methylcyclohexane at 85 8C for 9-10 hours resulted in the formation of the 4-phenylcoumarins in moderate yields (Scheme 1). Surprisingly, the reaction of aryl-2-butynoates also was successfully performed to afford the corresponding coumarin in an excellent yield (89 %; Scheme 1).…”

“…In particular, Sc(OTf) 3 , In(OTf) 3 , and Hf(OTf) 4 effectively catalyzed the alkenylation of the electron-deficient alkynes, such as p-tifluoromethylphenylacetylene and pchlorophenylacetylene, which were totally inactive without the presence of an ionic liquid (entries 14-18). [3] Similarly, the reaction of arenes with ethyl phenylpropiolate in the presence of Hf(OTf) 4 6 ] a conversion of only < 5 % was observed. It should also be noted that the ionic liquid phase containing the metal triflate could be readily recovered by simple decantation of the organic layer (the upper phase) after reaction.…”

“…[2] Well-known Lewis acidic metal chlorides, such as ZrCl 4 and AlCl 3 , produce the desired alkenylated products but in extremely low yields (for example, 1 and 6 % yields of 1-phenyl-1-(p-xylyl)ethene for the reaction of p-xylene with phenylacetylene at 85 8C, respectively). [3] Recently, a number of catalysts, such as the solid acid zeolite HSZ-360, [4] phenoxymagnesium bromide, [5] and SnCl 4 /NBu 3 , [6] were found to be active for the ortho selective alkenylation of phenols with a limited range of alkynes (only aryl-substituted terminal alkynes underwent this reaction). It has been also found that GaCl 3 can promote the alkenylation of arenes with silylethyne, but excessive amounts of this Lewis acid (3 equiv) are required.…”

“…4 10 70 [c] [a] All reactions were carried out with an alkyne (1 mmol), an arene resulted in the alkyl-substituted alkynes usually undergoing self-oligomerization rather than the desired alkenylation reaction. Intramolecular alkenylation allowed us to synthesize 2(1H)-quinolinones from the corresponding aryl amides of phenylpropiolic acid in good yields (Scheme 2).…”