| Abstract
| - Polysubstituted tetrahydropyrans and thiacyclohexanes were synthesized in high yields withexcellent diastereoselectivities via indium trichloride mediated cyclizations between homoallylalcohols and mercaptans with aldehydes. In the case of tetrahydropyran products, the stereochemistry of the product was found to be directly correlated with the geometry of the homoallyl alcohols;whereas the cross-cyclization of aldehydes with trans-homoallyl alcohols generated (up-down-up)2,3,4-trisubstituted tetrahydropyran products exclusively, the reaction of aldehydes with cis-homoallyl alcohols provided mainly (up-up-up) 2,3,4-trisubstituted products. When a trisubstitutedhomoallyl alcohol was used, its cross-cyclization with aldehydes generated (up-down-up-down-up)pentasubstituted tetrahydropyran derivatives with simultaneous controlling of five stereogeniccenters. On the other hand, a cyclization−decyclization equilibrium was observed in the formationof thiacyclohexanes. The reaction of both cis- and trans-homoallyl mercaptans with aldehydesprovided the same major diastereomers.
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