The highly selective formation of biaryls by the cyclization of arylethynes catalyzed by vanadyl phthalocyanine

Abstract

The dimerization of arylethynes catalyzed by vanadium phthalocyanine to give substituted biaryls has been investigated. The reaction yield is always high and for many examples is only slightly affected by the aryl substituents. This fact is also related to the results obtained with metalloporphyrins, which give lower selectivities due to the presence of variable amounts of triphenylbenzenes.

An efficient approach to the cyclotrimerisation of alkynes: solvent-free synthesis of 1,3,5-trisubstituted benzenes using p-toluenesulfonic acid monohydrate

“…Significantly, the desired products could be obtained in higher yields from electron rich than from electron poor alkynylsilanes. Moreover, the desilylative cyclotrimerizations of the aromatic alkynylsilanes 1e, 1g, 1h and 1l (R 1 = 4-MeC 6 H 4 , 4-EtC 6 H 4 , 4-n-PrC 6 H 4 and 3-MeC 6 H 4 ) also proceeded smoothly to afford benzene derivatives 2c, 2d, 2e and 2h in high yields with complete regioselectivity ( 29 In addition, the aliphatic alkynylsilanes 1n, 1p and internal alkyl alkyne 1o in the presence of 1.0 equiv p-TsOH·H 2 O also underwent a cyclotrimerization smoothly to give the products 2j, 2l and 2k in 83%, 86%, and 85% yields, respectively ( Table 2, entries 14-16). Furthermore, the terminal alkynes 1b, 1d, 1f and 1k also gave the desired results, providing the benzene derivatives in high yields (Table 2, entries 2, 4, 6 and 11).…”

Phthalocyanine Metal Complexes in Catalysis

“…Vanadyl Pc catalyzed the cyclization of arylethynes . Interestingly, while Rh and Ru porphyrins afforded cyclotrimers, VOPc selectively provided cyclodimerization products, especially when Ar bears electron-donating substituents (Scheme ).…”

Regioselective Synthesis of 1,3,5-Substituted Benzenes via the InCl3/2-Iodophenol-Catalyzed Cyclotrimerization of Alkynes

“…Moreover, the cyclotrimerizations of alkynes 1 g – j (R 1 = 4-MeC 6 H 4 , 4-EtC 6 H 4 , 4- n PrC 6 H 4 , and 3-MeC 6 H 4 ) also proceeded smoothly to afford benzene derivative 2g – j in excellent yields with complete regioselectivity (Table , entries 7–10). However, the cyclotrimerizations 1k did not form the desired benzene derivative 2k (Table , entry 11), presumably due to the steric effect of the substituent in the ortho -position of 1k . Additionally, alkynes bearing a heterocyclic aromatic substituent such as 2-ethynylthiophene 1 l were found to afford the desired product 2l in 60% yield (Table , entry 12).…”