Copper catalysis addition with

Although the resulting vinylallenes 48 were usually obtained as mixtures of the E and Z isomers, complete stereoselection with regard to the vinylic double bond was achieved in some cases. In addition to enyne acetates, the corresponding oxiranes (e.g. 49) also participate in the 1,5-substitution (Scheme 2.18) and are transformed into synthetically interesting hydroxy-substituted vinylallenes (e.g. 50) [42], Moreover, these transformations can also be conducted under copper catalysis by simultaneous addition of the organolithium compound and the substrate to catalytic amounts of the cuprate (see Section 3.2.3). 

The conjugate addition of organometallic reagents R M to an electron-deficient alkene under, for instance, copper catalysis conditions results in a stabilized car-banion that, upon protonation, affords the chiral yS-substituted product (Scheme 7.1, path a). Quenching of the anionic intermediate with an electrophile creates a disubstituted product with two new stereocenters (Scheme 1, path b). With a pro-chiral electrophile, such as an aldehyde, three new stereocenters can be formed in a tandem 1,4-addition-aldol process (Scheme 1, path c). 

Unactivated aUsynes 209 undergo the addition of aryhnagnesium reagents under cooperative iron and copper catalysis, yielding trisubstituted alkenyhnagnesium species. They can be trapped with electrophiles, giving tetrasubstituted alkenes such as 210. In some... 

For the aziridination of 1,3-dienes, copper catalysis gave better yields of A-tosyl-2-alkenyl aziridines with 1,3-cyclooctadiene, 1,4-addition occurred exclusively (50%) [46]. Good results were also obtained on rhodium catalysed decomposition of PhI=NNs (Ns = p-nitrophenylsulphonyl) with some alkenes the aziridination was stereospecific, whereas with chiral catalysts asymmetric induction (up to 73% ee) was achieved. However, cyclohexene gave predominantly (70%) a product derived from nitrene insertion into an allylic carbon-hydrogen bond [47]. 

Tlie latter reagent undergoes 1,2-addition to a,p-unsaturated aldehydes 1,4-addition, with copper catalysis, is observed with cyclohexenone alone. A more satisfactory reagent for the conjugate introduction of the hydroxymethyl group is the allyldimethylsilylmethyl Grignt reagent... 

The number and type of copper centers, EPR parameters, and the two relevant absorption bands in the visible region for several representative members of the blue oxidases are listed in Table II. All laccases except that of the P. radiata enzyme contain four coppers per molecule with one type-1, one type-2, and one type-3 copper center. The EPR and absorption parameters resemble each other very much. Phlebia radiata laccase is supposed to contain only two coppers with one type 1, one type 2, and one PQQ per mole (70). This is quite unusual and will be discussed critically below, since it is possible that the copper content determined for this enzyme is inaccurate. Ascorbate oxidases have eight coppers per homodimer with two type-1, two type-2, and two type-3 copper centers. Ceruloplasmin typically contains six to seven copper ions per molecule with three type-1, one type-2, and one type-3 copper centers. It has also been proposed that there are only two type-1 copper ions and a new type-4 copper that is presumed to exhibit no EPR signal. In addition there is a variable content of chelatable copper. It is responsible for copper contents exceeding 6 coppers/mol but does not seem to be required for catalysis. It is now generally accepted that ceruloplasmin has three type-1 copper centers and the reason for this will be discussed below. 

Copper(I) halides have been shown previously to accelerate the formation of (Z)-3-iodoprop-2-enoic acid. ,8,9,io xhe formation of the (E)-isomer during these low temperature investigations indicated that, at higher temperature, copper catalysis could accelerate the formation of the thermodynamically favored (E)-isomer. Therefore, we decided to investigate the effect of temperature on the copper-catalyzed addition of HI to propiolic acid, with a view to creating a copper-catalyzed, one-step synthesis of the (E)-isomer. 

The iodine-zinc exchange of an alkyl iodide with EtjZn is proi oted by the addition of small amounts of copper(I) salts such as CuCN or Cul. Although the exact reason for this copper catalysis is now known, it has been speculated that the presence of copper(I) salts promotes a radical chain-reaction resulting in the formation of a dialkylzinc species (Scheme 9-32) [22b]. Similarly, the addition of other transition metals such as nickel and palladium salts promotes radical reactions. 

The 1,4-addition of Grignard reagents under copper catalysis, followed by a trap of the resulting (magnesium) enolates with an appropriate electrophile, is a versatile method for double functionalization or double carbon-carbon bond formation at the a- and / -positions of an olefinic bond that bears a carbonyl group [Eq. (89)]. Recently, this topic has been extensively reviewed [155]. Examples [170,173,174] of this notion are presented in Eqs. (77), (90) [170], and (91) [174]. 

Severe limitations on the usefulness of the classical Wurtz reaction in the production of cross-coupled products have led to the development of many more generally useful variants. In particular, the use of copper catalysis and of stoichiometric organocuprate species have proved very valuable. The reactions of ir-allylnickel halides with sp halides is also represented by equation (1), and the uses of these reagents are treated separately. In order to provide a balanced view of the value of ir-allylnickel halides, some additional reactions with centers other than sp are described. 

By derivatizing an a,p-unsaturated acid into the mono ester of chiral 1,1 -bi-8,8 -naphthol the reaction with lithium dialkylcuprates leads to saturated ketones containing chirality centers at the p-carbon atoms." Consecutive 1,4-addition and 1,2-addition account for this result. The alkyl transfer to enones from Grignard reagents under copper catalysis is subject to chiral modification, e.g., by the introduction of 56" or 57." ... 

Copper catalysis for particulate removal from diesel exhaust gas. Copper fuel additives in combination with copper coatings. 

It is now usual to promote these cycloadditions by catalysts for example, reaction with A -tosyl-ynamides, using ruthenium or copper catalysts, giving 1-substituted 5- and 4-amino triazoles, respectively the formation of the 1,4-substitution pattern with copper catalysis and 1,5-pattem with ruthenium catalysis seems to be general. The latter metal will also promote addition to internal alkynes. ... 

Effects of a series of transition metal stearates, the concentration of the copper stearate, the solvent, various additives, and other factors on the thermal oxidation of polypropylene were studied in trichlorobenzene solution. The mechanism of copper catalysis is discussed. The order of decreasing catalytic activity of the metal stearates was Cu > Mn > Fe > Cr > Al Ni Co control Ti >> Zn >> V. The addition of propionic acid to the solvent accelerated the oxidation of the polymer. The presence of the copper leveled off oxygen uptake of the polymer after a certain time. The amount of oxygen absorbed decreased with increasing concentration of the copper, and at higher concentration (7.9 X 10 3M) the polymer oxidation was inhibited. 

In this chapter, the effect of a series of transition metal stearates on the thermal oxidation of polypropylene in homogeneous solution is examined, and the results obtained are compared with that in bulk reported previously (16). In addition, the effects of the anion of copper compounds, the concentration of copper, the solvent, and the additives on the copper compound-catalyzed thermal oxidation of polypropylene are studied, and the mechanism of the copper catalysis in solution is discussed. 

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