Photoreactions of β-aziridinylacrylonitriles and acrylates with alkenes: formation of head-to-head adducts and application to the preparation of pyrrolizidine alkaloid

The photochemical C,C-bond cleavage of N-benzyl β-aziridinylacrylonitrile and acrylate and the subsequent [3+2] cycloaddition with electron-deficient alkenes afforded head-to-head adducts selectively and efficiently. Irradiation of N-phenyl aziridine with acrylonitrile gave adducts, but photoreaction of N-benzoyl aziridine and thermal reactions of and with alkenes yielded C(γ),N-cleaved products instead of cycloadducts. N-trityl aziridine also reacted with electron-deficient alkenes, affording 2,3-cis-pyrrolidine derivatives exclusively. A formal synthesis of a pyrrolizidine alkaloid, isoretronecanol (), starting from was achieved in a convenient manner.