Intramolecular hydrogen abstraction promoted by amidyl radicals. Evidence for electronic factors in the nucleophilic cyclization of ambident amides to oxocarbenium ions.
A tandem 1,5-hydrogen atom transfer/radical oxidation/nucleophilic cyclization mechanism is proposed for the intramolecular hydrogen abstraction reaction promoted for primary carboxamidyl radicals. The electron-withdrawing capacity of the C-5 substituent can switch the reaction to give exclusively bicyclic spirolactams (6-oxa-1-azaspiro[4.5]decan-2-one) when R(1) = H or spirolactones (1,6-dioxaspiro[4.5]decan-2-one) when R(1) = OAc. With a substituent of medium polarity (R(1) = OMe), a mixture of lactones and lactams is formed.
Martín
Angeles
A
Instituto de Productos Naturales y Agrobiología del C.S.I.C., Carretera de La Esperanza 3, La Laguna, Tenerife, Spain.
Pérez-Martín
Inés
I
Suárez
Ernesto
E