Allylic alkylation copper catalysis

Zinc homoenolate reacts with allylic halides and diene monoepoxides under copper catalysis [29]. Treatment of the zinc nomoenolate with a catalytic amount of Cu(II) in a polar solvent (e.g. hexamethylphosphoramide, HMPA, N,N-dimethylacetamide, DMA) generates a copper species which undergoes clean Sn2 allylation reactions Eq. (40). Polar solvents not only accelerate the reaction but greatly improve the SN2 selectivity. A variety of allylating reagents can be employed in this reaction (Table 9). The SN2 /SN2 ratio is particularly high (close to 100%) when the alkylated carbon bears no substituents. The reaction of... 

Chelucci, G., Muroni, D., Pinna, G. A., Saba, A., Vignola, D. Chiral 2-(2-phenylthiophenyl)-5,6,7,8-tetrahydroquinolines new N-S ligands for asymmetric catalysis. Palladium-catalyzed allylic alkylation and copper-catalyzed cyclopropanation reactions. J. Mol. Catal. A Chemical 2003, 191, 1-8. 

Scheme 3.3 Domino conjugate reduction-allylic alkylation reaction catalysed by a combination of copper catalysis and chiral palladium catalysis.

Cyano compounds liquid crystals, 12, 278 in silver(III) complexes, 2, 241 Cyanocuprates, with copper, 2, 186 Cyano derivatives, a-arylation, 1, 361 Cyanosilanes, applications, 9, 322 Cyclic acetals, and Grignard reagent reactivity, 9, 53 Cyclic alkenes, asymmetric hydrosilylation, 10, 830 Cyclic alkynes, strained, with platinum, 8, 644 Cyclic allyl boronates, preparation, 9, 196 Cyclic allylic esters, alkylation, 11, 91 Cyclic amides, ring-opening polymerization, via lanthanide catalysis, 4, 145... 

Some examples to illustrate these categories are listed in Table 8.1. Many examples of reactions between organomagnesium compounds and organic halides are tabulated in General Ref. [A] it should be noted, however, that for many of the earlier experiments, transition metals may have been present as impurities in the magnesium used. While under some circumstances transition metal catalysis may be beneficial, under the conditions commonly used in the early experiments it usually led to a proliferation of products. For reactions with primary alkyl and allylic halides, catalysis with copper(i) salts is often beneficial examples of such reactions are also shown in Table 8.1 and a procedure follows. 

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