Photoreactions of bicyclic aziridines with alkenes and alkynes: a novel synthetic methodology for 8-azabicyclo[3.2.1]octane derivatives

The photochemical C-C bond cleavage of bicyclic aziridines 7 and subsequent [3 + 2] cycloaddition with electron-deficient alkenes and alkynes afforded the novel head-to-head adducts selectively and efficiently. The adducts contain the naturally occurring 8-azabicyclo[3.2.1]octane skeleton (e g. tropane alkaloids). The aziridine 8 fused with a 6-membered ring also afforded the cycloadducts but in poor yields. The methylaziridine 9 reacted with an electron-deficient alkene, affording the head-to-tail adduct 23 in addition to head-to-head adducts 22a and 22b. The photoreactions of bicyclic aziridines with alkenes and alkynes indicate a similar behavior to that of aziridines with a linear chain.