ISOMERIZATIONS OF CYCLOALKENE-DERIVED AND BICYCLOALKENE-DERIVED ACHIRAL EPOXIDES BY ENANTIOSELECTIVE ALPHA-DEPROTONATION

Enantioselective a-deprotonation-rearrangement of cis-cyclooctene oxid e 1 using organolithiums in the presence of(-)-sparteine 4 or (-)-alph a-isosparteine 5 gives the (-)-alcohol 2 in good yields and ees, The u se of C-2-symmetric bisoxazolines (-)-6a-d as ligands allows access to the (+)-alcohol 2. (-)-alpha-Isosparteine 5 functions as an efficient asymmetric ligand catalyst in the rearrangement of 1., The a-deproton ation process can be extended to other cycloalkene-derived achiral epo xides 7, 9, 11, 15 and 19. Lithium amide-induced transformations of ri gid bicycloalkene-derived epoxides (25, 34 and 42) are described, prov iding insight into the rearrangement mechanisms which operate followin g a-lithiation in such systems. The enantioselective a-deprotonation-r earrangement of bicycloalkene-derived epoxides (25, 29 and 42) to keto nes (28, 33 and 44 respectively) is described.