Stereocontrolled Synthesis of Cyclic Ethers by Intramolecular Hetero-Michael Addition. 6. A Computational Study of the Annelation to 2,3-Disubstituted Tetrahydropyrans

• DOI: 10.1021/jo961925t
• Publication Date: 2002-07-26T05:11:30Z
• Authors: Miguel A. Ramírez; José M. Padrón; José M. Palazón; Víctor S. Martín
• Keywords: Annulation; Transition state; Base (topology); Basis (linear algebra)

A computational study at the ab initio level of cyclization (E)- and (Z)-7-hydroxy-4-substituted-2,3-unsaturated esters leading to 2,3-disubstituted tetrahydropyrans has been performed. The showed requirement coordination between pre-tetrahydropyranyl oxygen that carbonyl α,β-unsaturated ester with cation base used obtain a suitable transition state model. calculations using 6-31G*//3-21G basis set show different relative stabilities for final products states them. 6-31+G* was as calibration less energetic states. model assuming pre-chair conformation locating chiral inductor equatorial approaching in axial mode E isomer Z geometry rationalizes experimental results. scope limitations applied 2,3,5,6-functionalized cases are discussed.