Stereoselective Cyclization Reactions Using Organotin Compounds

通过对“有机锡化合物立体选择性环化反应”的研究，得到了以下结果。通过有机锡化合物与LTA的氧化取代反应，得到相应的含氧官能团化合物。将该氧化反应应用于4-亚甲基丁烯内酯的合成。5-锡基-1，3-戊二醇衍生物经LTA处理后得到4-羟基四氢吡喃，产率较高。分子中有双键或三键的二元醇进一步环化成多环醚。3-羟基-5-锡基-戊酸经环合反应得到4-羟基-β-内酯。黄药在三丁基锡氢化物作用下自由基环化，得到一种易于氧化为内酯的亚硫内酯。环化反应的非对映选择性得到了很好的控制(95%)。具有两种自由基受体位置的线形黄原酸酯也环化成多稠硫内酯(串联自由基环化)。还进行了路易斯酸诱导的环氧烯丙基锡烷的区域和立体选择性环化反应。环合反应以良好的产率进行，环合反应的区域选择性取决于所形成的碳正离子的稳定性。还讨论了环氧碳的立体化学。

The following results were obtained from the study of "Stereoselective Cyclisation Reactions Using Organotin Compounds".1). By the oxidative substitution reactions of organotin compounds with LTA gave corresponding oxygen-functionalized one. This oxidation was applied to the synthesis of 4-ylidenebutenolides. Treatment of 5-stannyl-1,3-pentandiol derivatives with LTA gave 4-hydroxytetrahydropyran in good yield. The diol which has a double or a triple bonds in its molecule were further cyclized to a polycyclic ether. The cyclization of 3-hydroxy-5-stannyl- pentanoic acid yielded 4-hydroxy-delta-lactone.2). The radical cyclization of xanthates using tri-n-butyltin hydride gave a thionolactone which was easily oxidized to its lactone. The diastereo- selectivity of the cyclization was well controlled (de> 95%). The linear xanthates having two kinds of radical acceptor sites also cyclized to multifused thionolactone (Tandem radical cyclization).3). Lewis-acid induced regio- and stereoselective cyclization of epoxy-allylic stannanes was also carried out. The cyclization proceeded in good yield, and the regioselectivity of the cyclization was governed by the stability of the carbocation which was formed. The stereochemistry around the epoxide carbons was also discussed.