Palladium-alkynyl complexes

The reaction of aryl(alkynyl)palladium complex with Cul in the presence or absence of PPh3 ligand causes formation of alkynylcopper and aryl(iodo)palladium complexes via transmetalation of the alkynyl ligand from Pd to Cu (Eq. 5.49). 

The alkynyl and iodo ligands of the aryl(iodo)palladium and aryl(alkynyl)-palladium complexes undergo mutual exchange at —30°C (Eq. 5.51) [183]. 

Exchange reactions of aryl and iodo ligands and of aryl and alkynyl ligands are not observed at all. Analogous alkynyl ligand transfer from aryl(alkynyl)palladium complexes to aryl(iodo)platinum complexes shown in Eq. 5.52 occurs above 35°C to cause complete alkynyl group transfer from Pd to Pt [183]. 

In the former case, the reachon of [PdAr(I)Ln], where L is electron-rich PEt3, was examined (Scheme 6.31). Here, the reachon between the palladium complex, with R = Me, and lequiv. of [Cu(CCPh)(PPh3)]4 led to 74% of the Sonogashira product along with unreacted starting material. When the palladium copper ratio was decreased to 1 2, full conversion to the coupling product was observed. The intermediate of this reachon, an aryl(alkynyl)palladium complex, was formed in 65% as its trans-isomer, when the reaction temperature was lowered to -30 °C. The... 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

The intramolecular addition of the O-H bond to alkynes catalyzed by palladium complexes has been developed by K. Utimoto et al. (Eq. 6.59) [104]. An alkynyl alcohol can be converted to a cyclic alkenyl ether in the presence of a catalytic amount of [PdCl2(PhCN)2 or [PdCl2(MeCN)2] in ether or THE at room temperature. When the reaction was carried out in MeCN-H20 under reflux in the presence of a catalytic amount of PdCl2, hydration of the acetylenic alcohol occurred and the ketoalcohol was obtained in good yield instead. 

A hydrosilylation/cyclization process forming a vinylsilane product need not begin with a diyne, and other unsaturation has been examined in a similar reaction. Alkynyl olefins and dienes have been employed,97 and since unlike diynes, enyne substrates generally produce a chiral center, these substrates have recently proved amenable to asymmetric synthesis (Scheme 27). The BINAP-based catalyst employed in the diyne work did not function in enyne systems, but the close relative 6,6 -dimethylbiphenyl-2,2 -diyl-bis(diphenylphosphine) (BIPHEMP) afforded modest yields of enantio-enriched methylene cyclopentane products.104 Other reported catalysts for silylative cyclization include cationic palladium complexes.105 10511 A report has also appeared employing cobalt-rhodium nanoparticles for a similar reaction to produce racemic product.46... 

Grignard reagents convert aromatic sulfonyl chlorides or aromatic sulfonates to sulfones. Aromatic sulfonates have also been converted to sulfones with organolithium compounds.1745 Vinylic and allylic sulfones have been prepared by treatment of sulfonyl chlorides with a vinylic or allylic stannane and a palladium-complex catalyst.1746 Alkynyl sulfones can be prepared by treatment of sulfonyl chlorides with trimethylsilylalkynes, with an AICL catalyst.1747... 

Organozinc reagents have been coupled with halides in the synthesis of dienes and other conjugated systems to form new carbon-carbon bonds such reactions have been reviewed477-479. In particular, the reaction of alkynyl zinc reagents with vinyl halides has been used in natural product synthesis, usually catalyzed by palladium complex catalysts. 

---