Nickel-catalyzed cyclodimerization

The reaction mechanism of nickel-catalyzed cyclodimerization has been investigated.10 The dimerization of buta-1,3-dienes is also possible with palladium salts.11... 

As well as formation of metallacyclobutenones, reactions of cyclopropenones with transition-metal compounds can lead to acetylene-derived products by decarbonylation, to quinones by a nickel-catalyzed cyclodimerization, and to cluster compounds involving a cleavage of the double bond of the cyclopropenone. ... 

We have previously used this method to establish allyl isomerization events in nickel catalyzed cyclodimerization of butadiene, and describe here our application to the polymerization mechanism. 

Metal-catalyzed cyclodimerizations of cumulenes can often result in different regiochemistry compared to their thermal counterpart. For example the nickel-catalyzed dimerization of the cumulene 22 gives exclusively the 4-radialene 23 whereas the thermal reaction gives the symmetrical 4-radialene 24.29 Metal-catalyzed cyclodimerizations of alkenes as seen in this and other examples often proceed under mild conditions. However, as the result of the intervention of metal-complexcd intermediates, regio- and stereochemistry may differ from their thermal counterparts. 

Homogeneous nickel complexes proved to be versatile catalysts in dimerization and trimerization of dienes to yield different oligomeric products.46-55 Depending on the actual catalyst structure, nickel catalyzes the dimerization of 1,3-butadiene to yield isomeric octatrienes, and the cyclodimerization and cyclotrimerization to give 1,5-cyclooctadiene and all-trans-l,5,9-cyclododecatriene, respectively46 56 [Eq. (13.13)]. Ziegler-type complexes may be used to form cis,trans,trans-1,5,9-cyclododecatriene37,57 58 [Eq. (13.14)], which is an industrial intermediate ... 

The first catalytic cyclodimerization of 1,3-butadiene (BD) to 1,5-cycloocta-diene using modified Reppe catalysts was reported by Reed in 1954 [4], and only two years later Wilke reported on the titanium-catalyzed synthesis of cyclo-dodecatrienes from BD [5]. It remained for Wilke and his co-workers to show the tremendous versatility and scope of the nickel-catalyzed cyclooligomerizations of... 

The nickel-mediated [4 + 4] cycloaddition strategy has also provided a concise and stereocontrolled route into the sequiterpene lactone (+)-asteriscanolide (128).The basic features of this approach are outlined in Scheme 17. The critical [4 + 4] cycloaddition step occurred under standard conditions to give the key intermediate in 67% yield. Clearly, the intramolecular version of the nickel-catalyzed diene cyclodimerization has been established as a powerful and highly-selective protocol for the synthesis of cyclooctane ring systems and should find extensive application to natural product synthesis. 

In earlier investigations, asymmetric nickel-catalyzed isomerization and cyclodimerization of methylenecyclopropane was found to give l-methylene-2-vinylcyclopentane44. The nickel catalyst system was prepared by reduction of NiBr2L2 with butyllilhium. With tributylphosphane as ligand a 91% yield of the dimerization product was obtained. With dibromobis(( - )-methyl(phenyl)propylphosphane]nickel and butyllithium, optically active (no enantiomeric excesses given) l-methylene-2-vinylcyclopentane of unknown absolute configuration was obtained in 30% yield. Involvement of a n-allyl intermediate is proposed (loc. cit. 141 in ref 45). 

Chiral aminophosphane-phosphinites (AMPP), prepared by the reaction of chloro(diphenyl)-phosphane with optically active amino alcohols, such as ephedrines, prolinol and A -methyl-phenylglycinol, are used as ligands in transition metal catalyzed cyclodimerization of butadiene to 4-vinylcyclohexene62,10 . With a nickel(0)LJ catalyst (L = Proliphos), (—)-4-vinylcyclo-hexene with 15% ee was obtained in 50% yield6. ... 

As illustrated in the early achievements from Reppe on the cyclotetramerization of acetylene and from Wilke on the cyclodimerization and cyclotrimerization of butadienes, nickel-catalyzed cycloadditions possess considerable potential in the construction of medium ring systems. Pioneering studies by Wender have demonstrated many practical implications that have advanced the... 

In 2010, Ohashi and Ogoshi found an interesting nickel-catalyzed [3+3] cyclodimerization of ester-substituted MCPs giving six- and five-membered ring derivatives (see (43)) [98]. 

Nickel(0)-catalyzed dimerization of isoprene (3 2-methylbuta-l.3-diene) has been used as the key step in the synthesis of (+)-grandisol (8), a male boll weevil pheromone. It is interesting to note that the cyclobutane 4 was formed by unsymmetrical and head-to-head cyclodimerization and that cycloadduets 5-7 were also formed in this transformation.9... 

These cyclodimerization and cyclotrimerization reactions are catalyzed by low valent Ziegler-type Ni catalysts (139—144). Large ligands, such as tris-o-biphenylyl phosphite on nickel tend to favor cydooctadiene (COD) formation while smaller ligands favor the linear dimer, 1,3,7-octatriene. The dimer yield at 80°C and 101.3 kPa (1 atm) is 96%. The nickel catalyst can also be placed on a support so that it can be recycled (145). Many other type catalysts have been reported for this reaction (146). The linear 1,3,7-octatriene and its 1,3,6 isomer are also obtained by a Pd catalyzed dimerization (147—151). The kinetics of thermally induced dimerization to COD has also been studied (152). 

Both bis(l,5-cyclooctadiene)nickel(0) and bis(acrylonitrile)nickel(0) catalyze the polymerization of allene to highly crystalline linear polymers (451). With compounds such as tri-o-tolyl phosphite, bis(acrylo-nitrile)nickel in hydrocarbon catalyzes the cyclodimerization of butadiene to 1,5-cyclooctadiene, whereas in alcohols it catalyzes the... 

In the case of tetramethylbutatriene, Ni(0) catalyzes not only the cyclodimerization (formation of [4]radialene 94), but also the cyclotrimerization, leading to [6]radialene 95 and its isomer 96 (see also Section ILD). The product pattern depends to some extent on the nature of the catalyst, but the choice of solvent seems to be more crucial. This is illustrated impressively by the Ni(cod)2-catalyzed reaction of 93, which leads exclusively to the [4]radialene in toluene solution, but to the [6]radialene in DMF. Interestingly, the stoichiometric reaction between 93 and (2,2Tbipyridyl)-(l,5-cyclooctadiene)nickel yields the nickel complex 97, which has been isolated and characterized by X-ray diffraction. On treatment of 97 with two equivalents of maleic anhydride, reductive elimination of nickel takes place and octamethyl[4]radialene (94) is formed in good yield. This reaction sequence sheds light on the mechanism of the Ni-catalyzed reactions mentioned above further ideas on the mechanism of the cyclodimerization and cyclotrimerization reactions have been developed by lyoda and coworkers. ... 

When phosphane-free nickel complexes, such as bis(cycloocta-l,5-diene)nickel(0) or te-tracarbonylnickel, are employed in the codimerization reaction of acrylic esters, the codimer arising from [2-1-1] addition to the electron-deficient double bond is the main product. The exo-isomer is the only product in these cyclopropanation reactions. This is opposite to the carbene and carbenoid addition reactions to alkenes catalyzed by copper complexes (see previous section) where the thermodynamically less favored e Jo-isomers are formed. This finding indicates that the reaction proceeds via organonickel intermediates rather than carbenoids or carbenes. The introduction of alkyl substituents in the /I-position of the electron-deficient alkenes favors isomerization and/or homo-cyclodimerization of the cyclopropenes. Thus, with methyl crotonate and 3,3-diphenylcyclopropene only 16% of the corresponding ethenylcyc-lopropane was obtained. Methyl 3,3-dimethylacrylate does not react at all with 3,3-dimethyl-cyclopropene, so that the methylester of tra 5-chrysanthemic acid cannot be prepared in this way. This reactivity pattern can be rationalized in terms of a different tendency of the alkenes to coordinate to nickel(O). This tendency decreases in the order un-, mono- < di-< tri- < tet-... 

A recently reported cyclodimerization reaction of butadiene is the formation of 2-methylenevinylcyclopentane 170 171>. The reaction is catalyzed most effectively by rra/jj-bis (triethylphosphine)chloro-(o-tolyl)nickel in the presence of alcohol. It is interesting that negligible amounts of cyclooctadiene and cyclo-dodecatriene are formed with this catalyst. 

The nickel(O) complex Ni4(CNBu07 catalyzes reduction of acetylenes to olefins, isocyanides and cyanides to amines, as well as cyclotrimerization of acetylene and cyclodimerization of butadiene. Reduction of isocyanides is also catalyzed by other clusters (Chapter 13). Isocyanide copper compounds catalyze addition of CH2CIY (Y = COOR, COR, CN) to olefins leading to the formation of cyclopropane derivatives... 

The thermal polymerization of butadiene yields, according to Ziegler et al., a mixture of vinylcyclohexene with at most 15% of cyclooctadiene (95, 96). In 1954 Reed (97) discovered the catalytic cyclodimerization of butadiene to cycloocta-1,5-diene with Reppe catalysts, with a 30-40% conversion at 120-130° C. Wilke et al. recently synthesized a very efficient class of catalyst. If nickel-acetylacetonate is treated with metal alkyls (especially aluminum alkyls) in the presence of electron-donating compounds (mainly cycloolefins), new tt complexes of nickel are obtained which catalyze the cyclo-oligomerization of butadiene (98, 99). Using cycloocta-1,5-diene as the olefinic component, the well-crystallized, faintly yellow bis(cycloocta-... 

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