Cu allylation

In the presence of Cu, allyl ethers can be coupled with Grignard reagents at room temperature in good yield and with high regioselectivity in favor of the 5 2 product, plus an excellent stereoselectivity toward the -isomer [53], when using a 1 3 Et O/THF mixture [Eq. (36)]. 

Elaborations of the oxazole scaffold included the first stepwise and mild functionalization performed through subsequent Mg or Zn metallation steps in positions 2, 4, and finally 5. The metallation allowed reactions with electrophiles, Negishi cross-couplings, Pd-catalyzed Negishi acylations, Sono-gashira couplings and, after transmetallation with Cu, allylations (130L6162). 

This is similar to the Friedel-Crafts method but is less harsh and has been proven successful at producing safrole. In a very small flask is added 7.2g of allyl chloride, 34.3g 1,3-benzodioxole and 0.15g powdered Cu (which can be made by... 

In contrast to oxidation in water, it has been found that 1-alkenes are directly oxidized with molecular oxygen in anhydrous, aprotic solvents, when a catalyst system of PdCl2(MeCN)2 and CuCl is used together with HMPA. In the absence of HMPA, no reaction takes place(100]. In the oxidation of 1-decene, the Oj uptake correlates with the amount of 2-decanone formed, and up to 0.5 mol of O2 is consumed for the production of 1 mol of the ketone. This result shows that both O atoms of molecular oxygen are incorporated into the product, and a bimetallic Pd(II) hydroperoxide coupled with a Cu salt is involved in oxidation of this type, and that the well known redox catalysis of PdXi and CuX is not always operalive[10 ]. The oxidation under anhydrous conditions is unique in terms of the regioselective formation of aldehyde 59 from X-allyl-A -methylbenzamide (58), whereas the use of aqueous DME results in the predominant formation of the methyl ketone 60. Similar results are obtained with allylic acetates and allylic carbonates[102]. The complete reversal of the regioselectivity in PdCli-catalyzed oxidation of alkenes is remarkable. 

With higher alkenes, three kinds of products, namely alkenyl acetates, allylic acetates and dioxygenated products are obtained[142]. The reaction of propylene gives two propenyl acetates (119 and 120) and allyl acetate (121) by the nucleophilic substitution and allylic oxidation. The chemoselective formation of allyl acetate takes place by the gas-phase reaction with the supported Pd(II) and Cu(II) catalyst. Allyl acetate (121) is produced commercially by this method[143]. Methallyl acetate (122) and 2-methylene-1,3-diacetoxypropane (123) are obtained in good yields by the gas-phase oxidation of isobutylene with the supported Pd catalyst[144]. 

An example of this reaction is the reaction of cyclohexene with t-butyl perbenzoate, which is mediated by Cu(I). " The initial step is the reductive cleavage of the perester. The t-butoxy radical then abstracts hydrogen from cyclohexene to give an allylic radical. The radical is oxidized by Cu(II) to the carbocation, which captures benzoate ion. The net effect is an allylic oxidation. 

Allyl chloride, Cu(0), Cu(C104)2 6H2O, Et20, 97% yield. ... 

Metallocorroles (M = Cu, Ni or Pd) can also be alkylated under the same conditions as the metal-free corroles23,24 to give the N2i-alkylated products together with a small amount of C3 alkylated product ( f = Pd). Allyl halides or bulky alkyl halides react with nickel corroles also at the 3-position. 

Auf analoge Weise erhalt man aus 5a-Acetoxy-6-oxo-5a-cholestan 50% d.Th. 6-Oxo-5a-cholestan. Bei der Reduktion von Allyl-athern mit Magnesium-bis-fdiathyl-cu-prat] erhalt man im wesentlichen unter C-O-Spaltung das entsprechende Aiken3. Die Reduktion verlauft i.a. ohne wesentliche Allyl-Umlagerung ab. 

A more direct access to the unstable and non isolated sulfonium ylides 58a- c is the reaction of diisopropyl diazomethylphosphonate 57 with allylic sulfides, catalyzed by Cu(II), Rh(II) [39], or ruthenium porphyrins.[40] For example, the a-phosphorylated y,d-unsaturated sulfides 59-61 are obtained through the [2,3] -sigmatropic rearrangement of 58a-c. This method allows the use of a greater variety of starting allylic sulfide substrates, such as 2-vinyl tetrahydrothiophene, or propargylic sulfides (Scheme 15). 

Hoveyda and coworkers [142] developed the Cu-catalyzed allylic substitutions of phosphonate derivatives with pyridinyl peptide structures as efficient ligands. The structure of the ligands was chosen through synthesis, and analysis of libraries. Optimized compounds were used as ligands for the... 

Scheme 1.64 Cu-catalysed allylic substitution of cinnamyl phosphate with ZnEt2 in the presence of P-aminosulfonamide ligands.

Scheme 1.66 Cu-catalysed allylic alkylations of allylic phosphates with vinylalumi-num reagents in the presence of sulfur-containing diaminocarbene ligands.

Scheme 1.83 Cu-catalysed substitutions of allylic acetates by RMgX with ferroce-nylthiolate ligand.

Cu-catalysed additions of ZnEt2 to Baylis-Hillman-derived allylic electrophiles with BINOL-based thioether ligand. 

Scheme 10.90 Cu-catalysed Grignard crosscouplings of allylic substrates with fer-rocenylthiolate ligands.

BF3 —Cu— R Conjugate addition, including acrylate esters and acrylonitrile S substitutionof allylic halides k... 

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