Silylcuprates reactivity

Scheme 3.1. Reactivity profile of silylcuprates with carbon electrophiles [14ej.

The reactivity of silylcuprates with oxabicyclic compounds was also examined [218, 223]. With oxabicyclo[2.2.1] compounds, addition and Peterson elimination to produce cyclohexadienes occurred as with silyllithium reagents, Eq. 200. 

Alkynes can be transformed into alkenylstannanes by reaction with stannyl-cuprates. It is possible to trap the 1,2-dimetallic alkene species with various electrophiles. The analogous vicinal difunctionalization of alkynyl selenides " has also been reported. A route to trisubstituted alkenes from phenylthioacetylene"" starts with cuprate addition, but a 1,2-metal rearrangment is involved. Enamines are obtained from N-ethynyldiphenylamine. The alkenylcopper intermediate is also reactive toward many electrophiles. Silylcupration of functionalized alkynes may lead to cyclic products by virtue of intramolecular alkylation. ... 

In summary, the higher-order silyl cuprates (1) and (3) tend to be more reactive and more nucleophilic than their lower-order counterparts in silylcuprations and SN2-like displacements. Both classes of reagents are fairly stable up to ambient temperatures. 

Copper(I) cyanide is not the only salt used to make silylcuprate reagents, any more than dimethylphenylsilyl is the only silyl group. The cyanide has the advantage that it is not hygroscopic, but in general it appears to make little difference to the reactivity... 

Dienes also react with the silylcuprate (1), but the intermediate copper species is inherently a mixture of regioisomers, summarized as (17). With reactive electrophiles, it gives mixture of regioisomers such as (18) and (19), but, with the less reactive electrophile aUyl diphenyl phosphate it gives only regioisomer (20) (eq 17). ... 

Extremely efficient and convenient ways to prepare alkenyl- and alkylsilanes are transition metal-catalyzed silylation of alkynes and alkenes respectively. A general mechanistic scheme should involve oxidative addition of Si-X (X = H, B, C, Si, Sn, S, and halgen) bonds to transition metal catalysts M followed by insertion of unsaturated bonds into either Si-M or X-M (M = transition metal) bond and reductive elimination (Scheme 3-22). On the other hand, highly reactive silylmetal reagents such as silylzincates and silylcuprates effect similar transformation without the aid of transition metal catalysts. 

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