Shen Wang, Wang Le
Cancer Research, Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, Illinois 60064-6101.
J Org Chem. 1999 Nov 26;64(24):8873-8879. doi: 10.1021/jo991116k.
The Stille reaction of 1,1-dibromo-1-alkenes 1 with aryl- and vinylstannanes produces different products depending on the reaction conditions. When the reaction is run in toluene or 1,4-dioxane with tris(2-furyl)phosphine (TFP) as the ligand, (Z)-bromoalkenes 2 are obtained stereospecifically in good to excellent yields with most substrates. However, 2-aryl-1,1-dibromo-1-alkenes (1e,1g) having an electron-donating methoxy group in the para- or ortho- position give poor yields. This method has been applied to the one-pot syntheses of stereospecifically trisubstituted alkenes 5. When the Stille reaction is conducted in a highly dipolar solvent (DMF), monobromides 2 and/or internal alkynes 4 are the products. The less reactive phenylstannane favors the formation of alkynes 4, regardless of which ligand is used. More reactive organostannanes (vinyl, furyl) require a very electron rich ligand, tris(4-methoxyphenyl)phosphine, for the formation of alkynes 4. This new method for internal alkyne preparation is general, requires very mild reaction conditions, and gives high yields.
1,1-二溴-1-烯烃1与芳基锡烷和乙烯基锡烷的施蒂勒反应根据反应条件会生成不同的产物。当反应在甲苯或1,4-二氧六环中以三(2-呋喃基)膦(TFP)作为配体进行时，对于大多数底物，能立体专一性地得到(Z)-溴代烯烃2，产率良好至优异。然而，在对位或邻位具有供电子甲氧基的2-芳基-1,1-二溴-1-烯烃(1e,1g)产率较低。该方法已应用于立体专一性三取代烯烃5的一锅法合成。当施蒂勒反应在高偶极溶剂(DMF)中进行时，产物为单溴化物2和/或内炔4。无论使用哪种配体，活性较低的苯基锡烷有利于炔烃4的形成。活性较高的有机锡烷(乙烯基、呋喃基)需要非常富电子的配体三(4-甲氧基苯基)膦来形成炔烃4。这种制备内炔的新方法具有通用性，反应条件非常温和，且产率高。
