Asymmetric Cyclization of x-Silyl Esters to Give Functionalized Hydrindanoncs

摘要

Intramolecular additions of 2-silyl esters, to carbonyl groups, also known as intramolecular Peterson olefmations, are rarely observed. In general, the starting materials for these reactions must be carefully selected so that the base does not removeone of the acidic protons adjacent to the carbonyl group. These competing deprotonations limit the utility of the Peterson olefination for cydization reactions. We here report on the first desilylations of alicyclc tncarhonyi compounds in which ester nolates are selectively formed and react further to yield functionalized hydnndanonex (5, 6) by means of a crossed, intramolecular aldol reaction. The cyclization products of these transformations are extremely important building blocks for the synthesis ofsteroids (for example the Hajos-Wiechert ketone).