Palladium alkynyl-alkenyl coupling

The palladium/copper-cocatalyzed coupling of the readily available trisubsti-tuted alkenyl(phenyl)iodonium triflates 77 with alkynyl- and alkenylstannanes proceeds under exceedingly mild conditions with retention of geometry of the alkenyl ligand of the iodonium salt (Scheme 35) [60]. 

The Suzuki Coupling, which is the palladium-catalysed cross coupling between organoboronic acid and halides. Recent catalyst and methods developments have broadened the possible applications enormously, so that the scope of the reaction partners is not restricted to aryls, but includes alkyls, alkenyls and alkynyls. Potassium trifluoroborates and organoboranes or boronate esters may be used in place of boronic acids. Some pseudohalides (for example triflates) may also be used as coupling partners. 

Palladium-catalyzed cross-coupling involving alkynylmetals and related alkynyl nucleophiles alkynyl-aryl, alkynyl-alkenyl, and alkynyl-alkynyl coupling... 

The Negishi palladium-catalyzed cross-coupling reaction of alkenyl, aryl, and alkynyl halides with unsaturated organozinc reagents provides a versatile method for preparing stereodefined arylalkenes, arylalkynes, conjugated dienes, and conjugated... 

Kang, S.K. Lee, H.W. Jang, S.B. Ho, P.S. (1996) Palladium-catalyzed cross-coupling reactions of aryl-iodonium, alkenyl-iodonium and alkynyl-iodonium salts and iodanes with terminal alkynes in aqueous-medium, Chem. Commun., 835-6. 

Palladium-catalyzed cross coupling of resin bound iodopyridine with a boronic acid (Suzuki reaction) (12) or with an alkenyl-, alkynyl-, or arylstannane (Stille reaction) (13) was effected by treatment of resin 5 with 4 equivalents of the boronic acid or stannane, 8 equivalents of K2CO3 (Suzuki reaction only), and catalytic Pd(PPh3)4 in DMF at 50 C for 20 hours. (14) Best results were achieved by running each reaction twice, with an intermediate wash of the resin, in order to drive the reaction to conq>letion. The corresponding Pd-catalyzed amination (Buchwald reaction) (15) worked well in protocol development but the reaction failed with the 3 amines attenpted during actual library preparation. 

The Suzuki-Miyaura reaction involves the palladium-catalyzed cross-coupling between organoboron compounds and halides. In most cases, aryl halides are used as electrophiles, but recent developments have broadened the scope and alkyl, alkenyl, and alkynyl halides can be successfully used as reaction partners. Among C—C coupling reactions, Suzuki-Miyaura reaction has become one of the most appealing because the reactants are air stable, nontoxic and tolerant of a variety of functional groups. 

Knochel demonstrated the effectiveness of soluble potassium or cesium alkoxides such as KO Bu or CsO Bu as well as KH in iV-methylpyrrolidinone (NMP) for promoting the 5-endo-dig cyclizations of 2-alkynylanilines to 2-substituted indoles in solution or the solid-phase <00AG(E)2488>. Alternatively, Cacchi coupled a palladium-catalyzed cyclization of o-alkynyltrifluoroacetanilides with the addition of benzyl bromide or ethyl iodoacetate to afford 2-substituted-3-benzyl or 3-indolylcarboxylate esters, respectively <00SL394>. Yamamoto reported a new palladium catalyzed indole synthesis in which 2-(l-alkynyl)-Ar-alkylideneanilines 117 give 2-substituted-3-(l-alkenyl)indoles 118 directly from the imine by the in situ coupling of an aldehyde with the alkynylaniline <00JA5662>. 

Palladium-mediated cydization based on the reactivity of o-alkynyl or alkenyl-phenyl isonitriles have been developed [105]. On the basis of their earlier studies on the three-component synthesis of allyl aryl cyanamides [106], Yamamoto and co-workers reported a palladium-catalyzed three-component coupling reaction of 2-alkynylisocyanobenzenes 122 with allyl methyl carbonate and trimethylsilylazide leading to N-cyanoindoles 125 [107]. One of the key steps of the proposed mechanism is the formation of 7i-allylpalladium carbodiimide 123 and its isomerization to rc-allylpalladium cyanamide complex 124 (Scheme 8.50). 

R = alkenyl, aryl, allyl, benzyl, propargyl R = alkenyl, aryl, alkynyl, alkyl, benzyl, allyl The Negishi Coupling was the first reaction that allowed the preparation of unsymmetrical biaryls in good yields. The versatile nickel- or palladium-catalyzed coupling of organozinc compounds... 

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