2-Trimethylstannyl-1 -alkenes

Coupling reactions.. A n Pli4PBr intercalated in mon bis(trimethylstannyl)alkenes wi with retention of configuration, equiv of the coupling reagent. ... 

Reduction of l,2-bis(trimethylstannyl)alkenes. Diimine generated in situ with hydrogen peroxide and CUSO4 catalyst (1%) is useful for the reduction. Vic-Silyl/ stannylalkene analogues are also hydrogenated. 

Additions to a,fa-acetylenic esters. Piers et alhave prepared a number of these reagents, and conclude that (trimethylstannyl)copper(I)-dimethyl sulfide, (CH3),SnCu-S(CH3)2 (1), is the best reagent of this type for conversion of 1-alkynes to 2-trimethylstannyl-l-alkenes (equation I) or for addition to ethyl 2-butynoate to... 

The addition of Cp2Zr(H)Cl, known as the Schwartz reagent [30], to different alkenes and alkynes is known to be a facile process [31]. Therefore, the hydrozirconation of a variety of readily available enynes 12 is among the first methods developed for the stereoselective preparation of dienyl zirconium reagents 13. This process is both completely chemo- and regioselective with a syn addition of the zirconium hydride across the alkyne [32] (Scheme 5). From the same intermediate, the Zr atom can be isomerized in its internal position such as in 15 via a zirconacyclopropene intermediate 14. Moreover, the addition of trimethylstannyl chloride to 14 led to the stannylated dienyl zirconocene 16 [33] (Scheme 5). 

E-1,4-bis(trimethylstannyl)-1,3-butadiene 174 bis(triphenylphosphane) palladium(O) 100 bombykol 64, 65 a-bond metathesis 37 9-borabicyclo[3.3.1]nonane 49 boron-zinc exchange 389, 396 (5)-(/ )-BPPFA 29 Bredt s rule 243 bromide-zinc exchange 404 1,4-bromoacetoxylation 366 1 -bromo-1 -alkenes 63 bromoboration of acetylene 51... 

Whether a cyclopropanation reaction is stereospecific or not, is often tested with (Z)- and ( )-but-2-ene, but of course, this problem also holds for other diastereomeric alkenes. The following carbenes, generated by direct irradiation of the corresponding a-diazocarbonyl compound, undergo stereo specific or highly stereoselective cycloaddition to (Z)- and ( )-but-2-ene methoxycarbonylcarbene,105-106 chloro-, bromo- and iodo(ethoxycarbonyl)carbene,107 eth-oxycarbonyl(trimethylsilyl)carbene,108 ethoxycarbonyl(trimethylgermyl)carbene,109 ethoxy-carbonyl(trimethylstannyl)carbene,109 ethoxycarbonyl(trimethylplumbyl)carbene,109 ethoxy-carbonyl trimethylmercuriojcarbene.1 10... 

---