Direct synthesis of previously inaccessible bridgehead azabicyclics by intramolecular cyclization of alpha-sulfonamido and alpha-sulfonimido radicals

Syntheses of the first bridgehead sultams and the only known bridgehead dis ulfonimide are described. Both approaches capitalize on the electrophilicit y of alpha -sulfonyl radicals and their propensity to undergo intramolecula r ring closure. Where double bonds are concerned, 5-exo and B-exo pathways operate preferentially as long as structural strain is not excessive. When the reaction center is a carbon-carbon triple bond, the first cyclization g ives rise to vinyl radicals that hold sufficient reactivity to capture solv ent benzene. In the case of 45, this sequential reaction leads importantly to the introduction of a styrene functionality sufficiently activated to al low a second ring closure to be kinetically feasible. The solid-state struc tural features of 12 and 17 have been elucidated by X-ray crystallographic methods. Despite key differences from the norm in the alignment of the nitr ogen lone pair relative to the adjacent sulfonyl groups, these compounds ex hibit good hydrolytic stability. For 13, generation of the alpha -sulfonami de carbanion is possible and regiospecific oxidation with chromyl acetate h as been achieved.