Stereoselective Cyclization Reactions Using Organotin Compounds

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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.