Phenylethyne, coupling with

Bromoquinoline (70), behaving similarly to a simple carbocyclic aryl bromide, was coupled with phenylethyne 121 to provide disubstituted ethyne 122 in 50% yield (2001JCS(P1)978). 

As far as we are aware, the azo coupling of an ethyne derivative was only investigated over half a century ago Ainley and (Sir Robert) Robinson (1937) investigated the reaction of phenylethynes (phenylacetylenes) with diazonium ions (Scheme 12-59). Unsubstituted phenylethyne did not give identifiable products with the 4-nitrobenzenediazonium ion, but with the more nucleophilic 4-methoxyphenyl-ethyne an azo compound (12.119) was formed. On reaction with water it gives an arylhydrazone of an a-ketoaldehyde (12.120). 

The alkyne 85 has been oxidatively dimerized with copper(I) salts giving and coupled with l-bromo-2-phenylethyne in the presence of copper (II) salts. The 9-phenacylcarbazole 88 was cleaved to 9-benzylcarbazole with strong aqueous alkali in hot glycol. 

Similarly terminal alkynes could be cross-coupled with aryl halides or trillates Thus, trimethylsilylethyne (R=TMS) was reacted with iodobenzene (X=I, Y=H) in the presence of a catalytic amount of Pd(0) and 1 mol equiv Ag20 to afford phenyl(trimethylsilyl)ethyne in 79% yield (eq 20) no phenylethyne formation was detected under these conditions. This technique was further extended to the polycondensation of bis(trimethylsilylalkynyl) compounds with diiodoarenes. ... 

Double couplings have been reported by Cummins [143] [bis(tributylstannyl)ethyne with aryl iodides], Tamao et al. [144] [tris(butylstannyl)phenylethyne with a dibromosilacyclo-pentadiene] and Diederich and co-workers [145] [tiis(butylstannyl)phenylethyne with an E-dibromoalkene]. Li et al. have obtained a bis(binaphthol) from a monoiodobinaphthol and bis(tributylstannyl)ethyne [146] in a yield of 66% (Scheme 4-42). 

We recently developed efficient synthetic routes to the required 1,3- and -1,4 - dichlorobenzene Cr( CO) 3 (2) complexes for the preparation of pol3rmers such as 1 [13]. Complex 2 can be further modified by photolysis in the presence of tributylphosphine to produce the new monomer 3 (Scheme I). A relative rate study between 2 and 3 showed the latter complex to be less reactive in the palladium-catalyzed cross-coupling reaction with 1-(trimethylstannyl)-2-phenylethyne. The palladiiun-catalyzed polycondensation of monomers 3 and 4 resulted in high yields of polymer 5 (>90%). A reaction temperature of 65 °C and the use Of THF as solvent proved to be the optimum polymerization conditions. Lower temperatures or a solvent change to toluene afforded little if any polymer after several hours of reaction. 

Cyclotrimerizations of phenylethynes using palladium-dppf complexes have been studied, and the coordination chemistry of l,T-bis(diphenylselenophosphoryl)ferrocene with gold and silver has been investigated. The novel l,l, 2,2 -tetrakis(diphenylphosphino)-4,4 -di-/ tt-butylferrocene-type phosphines may be used as ligands in palladium-catalyzed Suzuki cross-coupling and Heck alkylation of aryl halides. 

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