Synthesis and anionically induced domino reactions of chiral alpha-bromo alpha,beta-unsaturated esters

The chiral alpha-bromo alpha,beta-unsaturated esters 3 and 9 are prepared by asymmetric Sharpless dihydroxylation (AD) of 5 and from ester 7 and the chiral diols 8 by transacetalization, respectively. Both types of alpha-bromo alpha,beta-unsaturated ester react with the kinetic Lithium dienolates of enone 10 to give functionalized tricyclo[3.2.1.0(2,7)]octanes 11. Esters 3 give one single diastereomer (de greater than or equal to 95%), whereas mixtures of diastereomers (de 28 to 46%) are obtained with the esters 9.