[58207-97-9] · C17H38SiSn · (E)-1-Tri-n-butylstannyl-2-trimethylsilylethylene · (MW 389.35)
Physical Data: bp 96-102 °C/0.5 mmHg.
Analysis of Reagent Purity: IR 1538 cm-1 (C=C); 1H NMR (CDCl3, CH2Cl2) d 0.12 (9H, s), 0.95 (9H, t, J = 7 Hz), 1.41 (18H, m), 6.65 and 7.08 (2H, AB pattern, J = 23 Hz).
Solubility: sol ethers, DMF, hydrocarbon, aromatic solvents.
Preparative Method: bis(tri-n-butylstannyl)ethylene is treated successively with molar equivalents of n-Butyllithium and Chlorotrimethylsilane to give (E)-1-tri-n-butylstannyl-2-trimethylsilylethylene.5
Handling, Storage, and Precautions: most tin compounds are toxic and are readily absorbed through the skin.4 Their preparation and use should be carried out at all times in a well-ventilated fume hood.
In general, (E)-1-tri-n-butylstannyl-2-trimethylsilylethylene undergoes the same types of Pd0-catalyzed cross-coupling reactions as other substituted vinylstannanes. It readily couples with vinyl halides in the presence of catalytic amounts of Pd0, giving 1,3-dienes in high yields (eq 1).6 Vinyl and aryl triflates can undergo the cross-coupling reactions with the organostannane reagent, yielding 1,3-dienes provided Lithium Chloride is also present (eq 2).7,8
When the coupling reactions of vinyl and aryl triflates are carried out in the presence of Carbon Monoxide and LiCl, good yields of the cross-coupled ketones are obtained (eqs 3 and 4).9 This is a particularly attractive route to divinyl ketones which are important substrates in the Nazarov cyclization.
The reagent also couples predominantly 1,4 to acyclic vinyl epoxides to give allylic alcohols. The regioselectivity is controlled by the substitution pattern of the vinyloxirane. The 1,4 versus 1,2 selectivity could be further enhanced by the addition of water (10 equiv based on the vinyl epoxide) (eq 5).10,11
For additional discussion about palladium-catalyzed coupling reactions, see also those entries dealing with organopalladium catalysis (e.g. Tetrakis(triphenylphosphine)palladium(0), Tris(dibenzylideneacetone)dipalladium, and (E)-1-Trimethylsilyl-2-trimethylstannylethylene.
Transmetalation of trimethylsilyl-2-trimethylstannylethylene at low temperature with BuLi affords trans-b-trimethylsilyllithium in high yield, as evidenced by derivatization of 2-methyldimedone isobutyl ether (eq 6).3,12-14
Kevin J. Moriarty
Rhône-Poulenc Rorer, Collegeville, PA, USA