作者:Ronaldo A Pilli、Valéria B Riatto
DOI:10.1016/s0957-4166(00)00351-7
日期:2000.9
to 2,5-disubstituted tetrahydrofuran derivatives by a Lewis acid-promoted reaction with allylsilanes. High trans selectivity (12:1) was obtained when hindered allylsilane 8 was employed. 5-Substituted lactol 16 was transformed into 2,5-cis-disubstituted tetrahydrofuran 17b (6:1 ratio) by a TiCl4-promoted intramolecular allyl transfer process. Additionally, 2,5-cis-disubstituted tetrahydrofuran derivatives
5-取代的内半缩醛1,通过用烯丙基硅烷路易斯酸促进的反应转化为2,5-二取代的四氢呋喃衍生物。当使用受阻烯丙基硅烷8时,获得高反式选择性(12:1)。通过TiCl 4促进的分子内烯丙基转移过程,将5-取代的乳糖醇16转化为2,5-顺式-二取代的四氢呋喃17b(比率为6:1)。另外,在将烷基锂加入内酯6之后,再用Et 3 SiH / BF 3,可以得到高产率和非对映选择性的2,5-顺式-二取代四氢呋喃衍生物。·OEt 2减少相应的半缩酮。