A new procedure for highly stereoselective and regioselective synthesis of 2-ethynyl-3-hydroxytetrahydropyran derivatives based on alkyne-Co2(CO)6 complex

Article abstract of DOI:10.1016/S0040-4020(97)10357-X

Treatment of trans-epoxides 3 with Co₂(CO)₈ gave the corresponding cobalt complexes, which were subsequently exposed to a catalytic amount of BF₃·OEt₂ at -78°C to provide exclusively cis-2-ethynyl-3- hydroxytetrahydropyran derivatives via endo mode cyclization pathway. cis- Congeners, cis-3 afforded the corresponding trans tetrahydropyran derivatives exclusively. This novel cyclization has been found to proceed with retention of configuration at the propynyl stereogenic center. Requirement for stereoselectivity in cyclization was discussed.