Alkene Coupling Reactions

In a palladium-mediated oxidative coupling reaction, alkenes such as methyl acrylate, acrylonitrile, or styrenes cyclize with 6- [(diinethylainino)methylene]amino -l,3-dimethyluracil to give the corresponding 6-substituted pyrido[2,3-[Pg.128]

Palladium-Catalyzed Cross-Coupling Reactions Alkene Metathesis... 

Syntheses of alkenes with three or four bulky substituents cannot be achieved with an ylide or by a direct coupling reaction. Sterical hindrance of substituents presumably does not allow the direct contact of polar or radical carbon synthons in the transition state. A generally applicable principle formulated by A. Eschenmoser indicates a possible solution to this problem //an intermolecular reaction is complex or slow, it is advisable to change the educt in such a way. that the critical bond formation can occur intramolecularly (A. Eschenmoser, 1970). 

Heck reaction, palladium-catalyzed cross-coupling reactions between organohalides or triflates with olefins (72JOC2320), can take place inter- or intra-molecularly. It is a powerful carbon-carbon bond forming reaction for the preparation of alkenyl- and aryl-substituted alkenes in which only a catalytic amount of a palladium(O) complex is required. 

The initial step of the coupling reaction is the binding of the carbonyl substrate to the titanium surface, and the transfer of an electron to the carbonyl group. The carbonyl group is reduced to a radical species 3, and the titanium is oxidized. Two such ketyl radicals can dimerize to form a pinacolate-like intermediate 4, that is coordinated to titanium. Cleavage of the C—O bonds leads to formation of an alkene 2 and a titanium oxide 5 ... 

The coupling reaction of aryl-alkenyl halides with alkenes in the presence of a palladium catalyst and a base is known as the Heck coupling (Scheme 9.4).6 Since the early 1980s, this type of coupling reaction has been used for die syndiesis of poly(arylenevinylene) and related polymers by polymerization of AB- or AA/BB-type of monomers (Scheme 9.5).7... 

The Pd-catalyzed coupling reaction of aryl-alkenyl halides widi alkenes in the... 

A cross-coupling reactions of terminal alkynes with terminal alkenes 32 supported on Merrifield-resin (Scheme 4.5) in the presence of Grubs ruthenium initiator [Cl2(PCy3)2Ru = CHPh] provided efficient access to supported 1,3-dienes 33 which were transformed into octahydrobenzazepinones 34 via MeAlCl2 catalyzed Diels-Alder reaction [27]. 

In these reactions a new carbon-carbon bond is formed, and they may be given the collective title coupling reactions. In each case, an aUcyl or aryl radical is generated and then combines with another radical (a termination process) or attacks an aromatic ring or alkene to give the coupling product. ... 

Aiyl diazonium salts can be used coupled with alkenes in a Heck-like reaction (14-20). Other reactive aryl species also couple with aryldiazonium salts in the... 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

Martin, Padron, and coworkers have reported on the scope and limitations of the use of iron(lll) halides as effective catalysts in the coupling of alkenes or acetylenes with aldehydes to achieve a wide variety of useful synthetic transformations. All these reactions are shown in Scheme 10, which serves as a guide through the aliphatic C-C bond formation section [27]. 

Iron-catalyzed C(sp )-C(sp ) bond-forming cross-coupling reactions of alcohols with alkenes has been reported by Tu and coworkers in 2009 [109]. Reactions of primary alcohols with various alkenes in the presence of a catalytic amount of FeCls in 1,2-dichloroethane afford the desired secondary alcohols as the crosscoupling products in moderate to good yields (Scheme 33). Iron sources such as... 

The hydrosi(ly)lations of alkenes and alkynes are very important catalytic processes for the synthesis of alkyl- and alkenyl-silanes, respectively, which can be further transformed into aldehydes, ketones or alcohols by estabhshed stoichiometric organic transformations, or used as nucleophiles in cross-coupling reactions. Hydrosilylation is also used for the derivatisation of Si containing polymers. The drawbacks of the most widespread hydrosilylation catalysts [the Speier s system, H PtCl/PrOH, and Karstedt s complex [Pt2(divinyl-disiloxane)3] include the formation of side-products, in addition to the desired anh-Markovnikov Si-H addition product. In the hydrosilylation of alkynes, formation of di-silanes (by competing further reaction of the product alkenyl-silane) and of geometrical isomers (a-isomer from the Markovnikov addition and Z-p and -P from the anh-Markovnikov addition. Scheme 2.6) are also possible. 

The Heck reaction consists in the Pd(0)-catalysed coupling of alkenes with an aryl or alkenyl halide or triflate in the presence of a base to form a substituted alkene (Scheme 7.1). The reaction is performed in the presence of an organopalladium catalyst. The halide or triflate is an aryl or a vinyl compound and the alkene contains at least one proton. 

Water-soluble phosphine ligands containing m-guanidinium moieties were synthesized and applied to aqueous Heck coupling reactions.149 High temperature appears beneficial for Heck-type coupling of simple alkenes in water.150... 

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