Organozinc copper-catalyzed

Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents... 

Feringa, B. L. Naasz, R. Imbos, R. Arnold, L. A. Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents. In Modem Organocopper Chemistry Krause, N. Ed. Wiley-VCH GmbH Weinheim, 2002 Chapter 7, pp 224—258. 

More attractive copper-catalyzed (mediated) transformations of allenes into alkynes were reported by Caporusso and co-workers [27f, 73-75], Allenes 142 were converted into alkynes 143 by treatment with stoichiometric amounts of a cuprate species, as exemplified in Scheme 14.35. The problem of regioselective formation of either alkyne 143 or allene 144 was solved by the proper choice of the organometallic species. Preferential formation of alkynes 143 could be achieved employing cuprates such as R3Cu(CN)ZnCl-LiCl, which are prepared from organozinc compounds. On the other hand, reactions of organomagnesium derived cuprates (R3CuBr)Mg-LiBr mostly provided allenes 144 as major components. 

Copper-Catalyzed Conjugate Addition of Functionalized Organozinc Reagents to a,p-Unsaturated Ketones Preparation of Ethyl 5-(3-Oxocyclohexyljpentanoate. 

Scheme 6.42. Copper-catalyzed allylic substitution of mesylate 197 with an organozinc reagent.

Tandem 1,4-addition to cycloalkenones constitutes an extremely versatile and elegant methodology for the synthesis of 2,3-disubstituted cycloalkanones, as is evident from its application in areas such as prostaglandin synthesis. Noyori et al. have reported the use of organozinc reagents in copper-catalyzed tandem additions [64]. The zinc enolate resulting from the catalytic enantioselective 1,4-addition of Et2Zn to cyclohexenone reacts readily with an aldehyde in a subsequent aldol condensation. 

I 7 Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents Tab. 7.4. Conjugate additions to 2,5-cyclohexadienone monoacetals and ethers. 

For enantioselective copper catalyzed addition of organozinc reagents to imines, see [97-116]. Enantioselective Ni-catalyzed alkyne, imine, triethylborane 3-component coupling has been reported, but modest selectivities (51-89% ee) are observed. For this method, vinylation is accompanied by ethyl transfer [149]... 

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