[58207-97-9] · C8H20SiSn · (E)-1-Trimethylsilyl-2-trimethylstannylethylene · (MW 263.08)
Physical Data: bp 22 °C/0.04 mmHg; nD 1.4723.
Solubility: sol ether, DMF, hydrocarbon, aromatic solvents.
Analysis of Reagent Purity: 1H NMR (CCl4/CH2Cl2) d 0.12 (s, 9H, Me3Si), 0.17 (s, 9H, Me3Sn), 6.30-7.20 (AB pattern, JAB = 22 Hz, 2H, vinyl).
Preparative Method: trans-1,2-bis(tri-n-butylstannyl)ethylene is treated successively with n-Butyllithium, Chlorotrimethylsilane, n-BuLi, and Chlorotrimethylstannane to give (E)-trimethylsilyl-2-trimethylstannylethylene in good yield.3
Handling, Storage, and Precautions: organotin reagents are extremely toxic and readily absorb through the skin.4 The reagent should be handled at all times in an efficient fume hood, wearing the appropriate personal safety equipment (i.e. gloves, safety eyewear).
Vinyl and aromatic halides undergo palladium-catalyzed cross-coupling reactions with trimethylsilyl-2-trimethylstannylethylene to give substituted 1,3-dienes and styrenes, respectively (eqs 1 and 2).5,6 Vinyl triflates also undergo cross-coupling reactions to give 1,3-dienes, provided that Lithium Chloride is added to the reaction (eq 3).7,8
The reactions employ mild conditions, are regioselective and stereospecific, and give high yields of products. In addition, tedious protection-deprotection steps are not necessary because the reactions tolerate a wide variety of functional groups.5,6
When the coupling of vinyl triflates is carried out in the presence of Carbon Monoxide and lithium chloride, carbon monoxide insertion occurs, yielding unsymmetrical divinyl ketones (eqs 4 and 5).9,10 This is a particularly useful procedure for the formation of intermediates for the Nazarov cyclization reaction.11
For additional discussion about palladium-catalyzed coupling reactions, see also those entries dealing with organopalladium complexes (e.g. Tetrakis(triphenylphosphine)palladium(0), Tris(dibenzylideneacetone)dipalladium, and/or (E)-1-Tri-n-butylstannyl-2-trimethylsilylethylene).
Transmetalation of trimethylsilyl-2-trimethylstannylethylene at low temperature with n-BuLi affords (E)-2-(Trimethylsilyl)vinyllithium in high yield (eq 6).3
Kevin J. Moriarty
Rhône-Poulenc Rorer, Collegeville, PA, USA