Stereospecific Syntheses Of 5-Alkyl-3-Ethoxy-2-((Phenylchalcogeno)Methylene)Tetrahydrofurans

2-Ethoxy-4-(phenylchalcogeno)but-3-ynyl ketones 1-10 were reduced with LiBH4 in Et(2)O diastereoselectively to give 5-(phenylchalcogeno)pent-4-yn-1-ols 11-20. Treatment of the phenylchalcogen-substituted alkynyl alcohols 11-20 with t-BuOK in t-BuOH provided useful (Z)-2-((phenylchalcogeno)methylene)tetrahydrofurans 21-31 stereoselectively.