Synthesis of Trisubstituted Furans from Epoxypropargyl Esters by Sequential SmI<sub>2</sub>-Promoted Reduction−Elimination and Pd(II)-Catalyzed Cycloisomerization
作者:José M. Aurrecoechea、Elena Pérez、Mónica Solay
DOI:10.1021/jo0014257
日期:2001.1.1
A two-step one-pot synthesis of 2,3,5-trisubstituted furans 8 from 4,5-epoxyalk-2-ynyl esters 6 is described. The sequence is initiated by a SmI2-promoted reduction that takes advantage of the ability of the alkynyloxirane moiety present in 6 to accept electrons from SmI2. The resulting organosamarium species then eliminates an adjacent acetate or benzoate leaving group, leading to the formation of
描述了由4,5-环氧烷-2-炔基酯6分两步一锅合成2,3,5-三取代的呋喃8。该序列由SmI2促进的还原反应启动,该还原反应利用6中存在的炔基环氧乙烷部分从SmI2接受电子的能力。然后,所得的有机sa物质消除了相邻的乙酸或苯甲酸酯离去基团,导致形成不稳定的2,3,4-三烯-1-醇7。未经分离,通过用催化量的四氢呋喃处理将其环化为呋喃8。钯(II)配合物和质子源。整个序列在温和的反应条件下进行。容许一些有用的官能团,例如氰基和α,β-不饱和酯,但是苄基和甲硅烷基保护的羟基在一定程度上被脱保护。使用乙炔,醛或酮和卤化乙烯片段的可靠反应,可以轻松地组装起始原料。这提供了在呋喃环的C-5处引入支链取代基的可能性。