Stereoselective E/Z-photoisomerization of cyclooctene using 2,4-pentanediol chiral tether

Abstract The photoisomerization, epoxidation, and cyclopropanation of chiral 2,4-pentanediol tethered cyclooctene were explored to examine the stereocontrollability of the tether. Photoisomerization of (2 R ,4 R )-2,4-pentanediol-tethered cyclooctene achieved a de of 20% at a high Z / E ratio of 0.80 at 25 °C, while (2 S ,4 R )-2,4-pentanediol-tethered cyclooctene yielded a lower de in spite of an even higher Z / E ratio. The epoxidation and cyclopropanation of 2,4-pentanediol tethered cyclooctene resulted in lower stereoselectivity compared with those of vinyl ether. We propose that the low de of the reactions of 2,4-pentanediol tethered cyclooctene is not attributable to the low stereocontrollability of 2,4-pentanediol tether, but due to the conformational multiplicity of the reactant site.