A set of allene-tethered benzoyloximes (5) has been treated
N atom to give the dihydropyridines 8. If the stannyl radical adds on the benzoyl moiety, an iminyl radical is formed with nBu 3 SnH. Depending on their substitution pattern, a wide range of compounds has been obtained. If the stannyl which leads to the 3H-pyrroles 9 and the alkylidenepyrrolines 10. Steric effects as well as polar effects are the radical adds on the allene, the C-centred radical thus formed undergoes either a 5-exo ring closure to give the factors governing the reaction course. cyclopentene derivatives 7 or a 6-endo ring closure onto the [a] Laboratoire Structure et Re ´activite ´des Espe `ces Paramagne ´tiques, CNRS UMR 6517: Chimie Biologie et Radicaux Libres.
As it seems to be of some importance in the product dis-Universite ´s Aix-Marseille I et III, tribution, we are going to discuss our results relative to the Avenue Escadrille Normandie-Niemen (boı ˆte 541); F-13397 nature of the R 3 substituent. For R 3 ϭ H, 5aϪd were prone Marseille Cedex 20, France Fax: (internat.) ϩ 33-4/91988512
to give the corresponding nitrile and benzoic acid, when E-mail: