The regioselectivity of the addition of benzeneselenyl chloride to 7-azanorborn-5-ene-2-yl derivatives is controlled by the 2-substituent: new entry into 3- and 4-hydroxy-5-substituted prolines

The electrophilic addition of benzeneselenyl chloride to the alkene moiety of 7-azabicyclo[2.2.1]hept-5-en-2-yl derivatives has been studied. With camphanates 8 and 9 N-Boc-5-endo-chloro-6-exo-phenylseleno-7-azanorborn-2-yl camphanates 10 and 11 are obtained with high regioselectivity due to a steric control. With N-Boc-7-azanorbor-5-en-2-one (2) the corresponding 6-endo-chloro-5-exo-phenylseleno derivative 15 is obtained in high yield due to a kinetic control attributed to the electron-releasing ability of the homoconjugated carbonyl group. Bicyclic adducts 10 and 11 and 15 are readily converted into 4-hydroxy-(14) and 3-hydroxy-5-substituted proline derivatives 19, respectively.