Stannyl cuprate

Stannyl cuprates couple widi vinyl halides or trlGales [16c-d, 85], and a vinyl stannane produced diis way has been used in die syntliesis of 7-[f )-alkylidetie]-cepbalosporlns [117]. Vinyl substitution reactions slariing Grom ddiydrofciraiis are... 

Scheme 3.33. Metalate rearrangement of a mixed vinyl(stannyl)cuprate derived from a 2,3-dihydrofuran (TIPS = triisopropylsilyl) [118b].

The western part 97 of tylosin aglycon (96), a 16-membered macrolide, has also been synthesized using this Kocienski metalate rearrangement [66]. Treatment of the lithiated dihydrofuran 99 with the stannyl cuprate [67] obtained from Bu3SnLi and CuCN, followed by Mel alkylation, exclusively gave the E vinyl stan-nane 100, in 80% yield. In the last stage, stannyl cupration [68] of the deprotected enyne diol 101 afforded the desired ( , E) stannyl diene 97 in 85% yield. 

Hydrostannation of 1-alkynes does provide vinyltins (equation 29), but these reactions may not be stereospecific or give the desired regiospecificity. Other methods from aUcynes are shown in equations 30 and 31 and Scheme 6. Stannyl cupration of allenes (using (Bus Sn)2CuLi or (Bus Sn)BuCuLi) also leads to allyl- and vinylstannanes. ... 

Propargyl derivatives R C=CCR2R3X (X = Br, AcO, MeS02, MeS03) react with stannyl cuprates to give allenes in high yield (unless the group R1 is very bulky), when... 

An improved method that uses stannyl cuprates instead of hexabutyldistannane and which react even with hindered vinyl triflates and give the coupling products in good yields121 is exemplified in equation 99. 

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. ... 

The use of stannyl cuprates [Cu(SnR3)2(CN)Li2] and [Cu(SnR3)(R )(CN)Li2] has also been developed by showing their regioselective syn addition to alkynes, the intermediate vinyl cuprate being eventually trapped with a variety of electrophiles 21-23,21.24... 

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