Boranes in synthesis - VII. Synthesis of 2-dialkylamino-6,6- dimethylbicyclo[3.1.1]heptan-3-ols from (R)-(+)-nopinone. Chiral auxiliaries for the addition of diethylzinc to aromatic aldehydes

Article abstract of DOI:10.1016/S0957-4166(97)00566-1

The reaction of (1R,5S)-(+)-nopinone with secondary amines in cyclohexane with the azeoptropic removal of water afforded excellent yields of the corresponding enamines. Hydroboration of these enamines with BMS followed by methanolysis and oxidation with basic hydrogen peroxide gave the corresponding (1R,2S,3S,5R)-2-dialkylamino-6,6-dimethylbicyclo[3.1.1]heptan- 3-ols. These amino alcohols, in spite of their trans geometry, served as chiral auxiliaries for the addition of diethylzinc to aromatic aldehydes to give nearly quantitative yields of the corresponding (R)-1-aryl-1-propanols with 52 to 80% ee.