Stereoselective Synthesis of Spiro[tetrahydropyran-3,3′-oxindole] Derivatives Employing Prins Cascade Strategy

A variety of aldehydes undergo smooth coupling with 4-hydroxy-N-methyl-2-methylene-N-phenylbutanamide in the presence of BF3·OEt2 under ambient conditions to produce the corresponding spiro-oxindole derivatives in good yields with excellent selectivity. It is an entirely new strategy to construct the spirocycles in a one-pot operation through a Prins cascade process.