Palladium catalysis olefinations

Similar results for the replacement of halogen on an olefinic linkage by phosphorus have been accomplished using dialkyl phosphites with palladium(O) catalysts.4179 Another reaction involving replacement of a vinylic halide by phosphorus utilizes palladium catalysis with a trimethylsilyl-substituted phosphine (Figure 6.19).80... 

Trost reported the synthesis of 1,4-dienes with ruthenium catalysis through regioselective carbometallation of alkynes with alkenes.51 Di- and trisubstituted olefins can also be obtained with arylboronic acids through an intermolecular process under rhodium,30 52 55 nickel,56 and palladium catalysis.57 Recently, Larock has reported an efficient palladium-catalyzed route for the preparation of tetrasubstituted olefins.58,59... 

To our knowledge, the first report on a coupling reaction of an organic tellurium compound promoted by palladium was published in 1977. Later on, LJemura reported that diphenyltellurium dichloride and phenyltellurium trichloride reacted with olefins under palladium catalysis to give stilbenes288 (Scheme 118). 

We reported that the palladium-catalyzed reaction of arynes with bis-jr-allyl palladium complex afforded 1,2-diallylated derivatives of benzene in good yields (Scheme 32) [77]. The reaction of 104 with allyltributylstan-nane 3a and allyl chloride 11 in acetonitrile in the presence of 2.5 mol % Pd2(dba)3.CHCl3/dppf catalyst at 40 °C for 12 h afforded 1,2-diallyl benzene 105 in 76% yield. The generation of benzyne 106 takes place presumably first from 104 under the conditions of the palladium catalysis, which reacts with the complex 2 in a manner similar to the diallylation of activated olefins (refer Scheme 29). 

The combination of ruthenium and palladium catalysis has been illustrated by the performance of the olefin metathesis—Heck coupling sequence [97,... 

The stereoselectivity of the reaction was the target of several investigations. The results clearly establish that the addition of hydrogen cyanide to olefins is stereospecifically syn [33, 46 9]. Thus, reaction of terminal, deuterium-substituted olefins yields the corresponding syn addition products. Hydrocyanation of 4-t-butyl cyclohex-1-ene with deuterium cyanide confirmed these results. It is found that the stereospecifity is independent of the catalyst metal employed, since both nickel° and palladium catalysis give the syn addition products [50]. 

The interpretation of the formation of the Ci3-lactone requires a sequence of mechanistical pathways which are unknown so far in rhodium-catalysis. Two proposals for the mechanism were given in Equation 12. The mechanism of path B is similar to that shown for palladium catalysis. A rhodium Cg-carboxylate complex is formed which under further incorporation of butadiene could yield the lactone. In the mechanism of path A three molecules of butadiene react with the starting rhodium compound forming a C- 2 Chain, which is bound to the rhodium by two n -ally1 systems and one olefinic double bond. Carbon dioxide inserts into one of the rhodium allyl bonds thus forming a C- 3-carboxyl ate complex, which yields the new C-13-lactone. 

Af-Heterocyclic carbenes and phosphine ligands can bind metal centers in a somewhat similar feshion via dative coordination using a lone pair of electrons. Therefore, phosphines are often considered to be the closest neighbors to NHCs in terms of organometallic chemistry. However, the properties of these two classes of compounds can be quite different, and can yield, for example, catalysts with quite different reactivity. The use of NHCs in olefin metathesis [25] and in palladium catalysis [26], for example, has allowed the preparation of highly active and stable species that are now at the forefront of their fields. Various studies have been conducted to explore the nature of bonding between NHCs and metal centers. Diez-Gonzalez and Nolan reviewed some aspects of NHC coordination to metal centers in 2007 [27]. 

Cyclic secondary amines are also produced by the ring expansion of O-sulphonyloximes via a Beckmann rearrangement/ the cyclization of a,aliphatic diamines by a ruthenium catalyst/ the palladium-promoted ring closure of amino-alkenes/ and the sulphonamidomercuration of 1,4- and 1,5-dienes. The latter two reactions form part of a wealth of new literature on the amination of olefins and acetylenes via aminomercuration " and via palladium catalysis. ... 

Alkenes and/or alkynes can be dimerized, telomerized, and polymerized under palladium-catalysis. In an effort to copolymerize polar co-monomers, Johnson et al. investigated catalysts based upon palladium. These catalysts were referred to as postmetallocene catalysts. They were based upon complexes bearing bulky, neutral, alpha-diimine (or diketimine) ligands. They have been commercialized as DuPont s Versipol olefin polymerization system. The commercial synthesis of 1-octene (starting in 2007) is a palladium-catalyzed telomerization of butadiene with methanol. ... 

Rennard and Kokes (39) in their paper stated directly that their purpose was just to study the catalytic activity of palladium hydride in the hydrogenation of olefins, in this case ethylene and propylene. Kokes (39a) in his article recently published in Catalysis Reviews summarizes the results of studies on such catalytic systems. 

Selective aromatic functionalization has been a permanent object of research since the ninenteenth century. Catalysis has offered a powerful tool to achieve this goal. Over the years we have worked out a complex catalytic system consisting of an inorganic compound such as a palladium salt and an organic molecule containing a strained double bond such as norbomene (1,2). We have seen that these two catalysts cooperatively react with an aromatic iodide, an alkyl iodide and a terminal olefin. The following equation reports an example (L = solvent and/or olefin) (3). 

Catalysis and Synthesis in the Laboratory. Research on the practical applications of catalysis was not matched in the laboratory. We began a study of metal and non-metal catalyzed reactions early in our sonochemistry program. Our first project was to develop a convenient method of hydrogenating a wide range of olefins. We chose formic acid as our hydrogen source and found it to be effective. For example, with continuous irradiation, palladium catalyzed hydrogenations of olefins are complete in one hour(44). 

CATALYTIC OXIDATION OF OLEFINS TO ALDEHYDES 10.6.1 Catalysis by Palladium Salts... 

A related cyclization of 2-(alkynyl)phenylisocyanates with terminal alkynes to oxindoles was also reported by the same group (Equation (115)).472 (E)-exo-olefinic oxoindoles are selectively obtained. It was proposed that a palladium acetylide generated by the C-H activation of terminal alkynes regioselectively inserts to the alkyne moiety and the resulting vinylpalladium intermediate adds to the C=0 part of the isocyanate to give a (Z)-oxindole. This (Z)-isomer is isomerized to the ( )-isomer under the reaction conditions through catalysis of the phosphine. 

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