REGIOSELECTIVE AND ENANTIOSELECTIVE ENOLISATIONS OF CYCLIC-KETONES USING CHIRAL LITHIUM AMIDE BASES

Enolisations of 3-methylcyclohexanone 16, and of a trans-fused perhydr oisoquinolone derivative 8, using several chiral lithium amide bases h ave been examined. In reactions involving a single enantiomer of the k etone 8, the use of a chiral base can result in enhancement or reversa l of the normal regioselectivity of enolisation to give the enol silan e derivatives 9 and 10, depending on the configuration-of the base use d. Similar matched and mismatched results are observed when (li)-3-met hylcyclohexanone, (R)-16, is treated with either enantiomer of the chi ral base 3. A new type of kinetic resolution, termed regiodivergent re solution, is observed when enolisation of the racemic ketones 8 or 16 is carried out using the chiral base 3.