Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• enantiomeric excess of only 25% e.e. while the enantiomeric purity of the starting diol 2a was 91% e.e. This result suggests that the selectivity for displacement of the two hydroxyl groups of 2a is only ca. 2 : 1 under these conditions. Examination of molecular models indicates that in order for the activated