Résumé
Abstract α‐Phosphorylated para ‐methoxybenzyl allenamides were oxidised with cerium(IV) to produce spirodienone lactams through a 5‐ endo ‐dig cyclisation. By modulating the electronic effects on the phosphorus and nitrogen atoms we were able to overcome some of the limitations of our first‐generation approach. Moreover, replacement of α‐allenylphosphonates with ynamido‐phosphonates led, in two steps, to the same spirodienone core after oxidation with cerium(IV) hence overcoming other limitations of the previous method.