Addition Reactions with Copper-Zinc Reagents

Organozinc copper reagents have very broad synthetic potential and a number of typical escperimental procedures have recently been published [99,100]. 

This reaction can be extended to cyanoketone dithioacetals [117]. Alkenyltellu- 

Sdieme 2.52. Cross-coupllrg of allyllc copper compourds. 

Transmetalation of Orgarto titanium and Orga nomanga nose Reagents 

Cross-coupling reactions between alkenylzirconocenes sndi as 133 and aryl or alkenyl iodides occur readily in the presence of CuCl and Pd(PPb3)4j producing tetrasubstituted olefins sudi as 134 in good yields (Sdieme 2.65) [141 142]. 

Addition Reactions with Copper-Zinc Reagents 

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Addition Reactions with Copper-Zinc Reagents... 

Scheme 2.41. Substitution reactions with copper-zinc reagents by addition-elimination mecha-...

SCHEME 87. Addition-elimination reactions of copper-zinc reagents with various Michael acceptors bearing a leaving group in h -position... 

Copper catalysed substitution reactions require high reaction temperatures and polar solvents like NMP.9 With activated alkenyl iodides bearing electron-withdrawing groups, copper-zinc reagents react readily leading to addition-elimination products.10-11 This method can be used to prepare a range of polyfunctional unsaturated molecules (Scheme 10.3).10-12... 

Another type of o-aminobenzyl synthon is based on o-(bis-trimethylsilylaminobenzyl)copper-zinc reagents <89TL4795>. These are prepared from the corresponding benzylic bromides by reaction with zinc, followed by addition of cuprous cyanide. These reagents react with acid chlorides to give 2-substituted indoles. Since the reactions proceed by C-acylation rather than iV-acylation, the conditions required for cyclization are mild and typically the C-acylated intermediates are not isolated. 

Exo-methylene ketones like 536 readily undergo addition reactions of various copper-zinc reagents. This methodology has been applied for the synthesis of prostaglandines such as 537 (Scheme 2-152, eq. (a)). Moreover, enantioselective Michael-additions have been pioneered by Feringa et a/. " and Alexakis et Remarkably, only a catalytic amount of the chiral ligand 538 (4 mol%) and Cu(OTf)2 (2 mol%) was required, and the 1,4-addition product 539 was obtained with an enantiomeric excess of 93% ee (Scheme 2-152, eq. This method was used for an... 

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