Nickel , catalysis

After successful use of arylboronate esters in the nickel-catalyzed 1,2-addition to aldehydes, Bouffard and Itami reported the use of unactivated ketones as substrates, as well as aldehydes, using Ni(COD)2/IPr HCl (IPr l,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) [58]. This system 

Baoeffl/, [59] andKappeefaZ. [60] independendy reported the synthesis of diarylmethanol derivatives using nickel catalysts, 2ildehydes, and arylboronic acid derivatives. While Bao and coworkers used Ni(C10, )2 OH O along with as base, with a maximum yield of 92%, Kappe and coworkers 

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Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

For this specific task, ionic liquids containing allcylaluminiums proved unsuitable, due to their strong isomerization activity [102]. Since, mechanistically, only the linkage of two 1-butene molecules can give rise to the formation of linear octenes, isomerization activity in the solvent inhibits the formation of the desired product. Therefore, slightly acidic chloroaluminate melts that would enable selective nickel catalysis without the addition of alkylaluminiums were developed [104]. It was found that an acidic chloroaluminate ionic liquid buffered with small amounts of weak organic bases provided a solvent that allowed a selective, biphasic reaction with [(H-COD)Ni(hfacac)]. 

This last one is now generally well accepted for the nickel catalysis. 

Fig. 12. Comparison of the Copper and Nickel catalysis on the arylation of alcohols...

A-methoxy-carbonyl-2-pyrroline 235 Michael reactions, nickel catalysis 97-8 monophospholanes with pendant f-BuS group 17,19... 

Similarly, nickel catalysis permits the extension of cross coupling to vinyl phosphates, which are in some cases more readily obtained and handled than vinyl triflates.273... 

Nickel catalysis has been used in a sequential synthesis of terphenyls, starting with 2-, 3-, or 4-bromophenyl neopentanesulfonates. Conventional Pd-catalyzed Suzuki conditions were used for the first step involving coupling of the bromide and then nickel catalysis was utilized for coupling the sulfonate. 

Keywords Allylation Carbonyl compound Dienes Homoallylation Nickel catalysis Reductive coupling... 

Scheme 1 Selective formation of allyl anion and homoallyl anion under nickel catalysis...

Several reports have been made of a successful catalyzed addition/ substitution reaction resulting in direct attachment of phosphorus to aromatic rings. The preparation of mixed triarylphosphines has been accomplished by the reaction of tin- or silicon-substituted diphe-nylphosphines with aryl halides catalyzed by palladium reagents.74 A similar transformation has also been reported using nickel catalysis.75 The addition/substitution of diphenylphosphine to triflate functionalized phenolic linkages has been of use for the preparation of substances as analogues of tyrosine-related amino acid derivatives, accomplished with catalysis by palladium acetate (Equation 4.29).76... 

Similarly, allenes [32] and alkynols [33] were used as starting materials and their carbonylation provides /3,y-unsaturated acids and unsaturated diacids, respectively. The specific reactivity of alkynols is explained by three formal steps during nickel catalysis (i) carbonylation of the triple bond leading to an acid containing an allylic alcohol moiety (ii) second carbonylation of the double bond to provide a hydroxydiacid and (iii) a dehydration step giving the corresponding unsaturated diacid (Scheme 2). 

Both the palladium- and the nickel-catalysis enables the use of allylic acetate as starting reagent. In the two approaches a zinc compound is evoked as key intermediate, though its formation has been demonstrated only indirectly. In the two methods allylic transposition is observed. The authors have then concluded that these electrochemical allylation reactions closely parallel the chemical allylation reactions involving allylzinc intermediates. 

Despite the excess of alkyne used, the transfer of only one vinylic group was observed. A more general approach of this method involves the reaction of (Z,Z)- and (f ,fi)-divinylic tellurides with alkynes under nickel catalysis, to give (Z)- and ( )-enynes with complete retention of configuration."... 

Another way of constructing axially chiral binaphthyls under nickel catalysis involves an enantioselective desymmetrization strategy. Thus, dinaphthothiophene... 

Metal catalytic activity may be expected to be a function of the solubility of the active species and/or the ease of electron transfer to the catalyst. The results given in Table IV show conclusively that the suggestion that catalysis occurs at a gas-solid interface (13) does not hold in these systems. Preliminary experiments showed that copper ion- and haemin-catalyzed systems oxidized rapidly with no trace of solid precipitation, and that cobalt and nickel catalysis were characterized by the production of colored solutions and precipitates. Filtration experiments showed these precipitates played only a small part in catalysis (Table IV). 

Hocek and coworkers studied the regioselectivity of the cross-coupling reaction between methyhnagnesium bromide and various dichloropurines. With 2,6- and 2,8-dichloropurines, it is possible to obtain the monomethylated product with an excellent regioselectivity (Scheme 33). It is important to notice that such a regioselectivity is not observed under palladium or nickel catalysis. 

Recently, this reaction has been extensively studied since it is currently the only method to couple aryl Grignard reagents with secondary alkyl halides Indeed, secondary aUtyl halides do not react under palladium or nickel catalysis . On the other hand, let us recall that the coupling of secondary alkyl Grignard reagents with aryl halides leads to poor results (see above). 

Reactivity of eiectrochemicaiiy prepared arylzinc compounds via a nickel catalysis... 

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