THE FIRST IRON-MEDIATED CATALYTIC CARBON-NITROGEN BOND FORMATION - [4+1] CYCLOADDITION OF ALLENYL IMINES AND CARBON-MONOXIDE

Catalytic carbon-nitrogen bond formation was achieved by iron carbonyls in the [4 + 1] cycloaddition of allenyl imines with CO. The Fe(CO)(5) photochemically catalyzed reaction of allenyl imines and CO gives preparatively useful yields of 3-alkylidene-4-pyrrolin-2-ones. These reactions take place under mild conditions and only require fluorescent light! Good control of alkylidene bond stereochemistry is achieved when the terminal allene groups are tert-butyl and methyl. Experiments in the dark show that stoichiometric Fe-2(CO)(9) can mediate [4 + 1] assembly by a purely thermal reaction to give good yields of the pyrrolinone products. These new methods for the construction of 3-alkylidene-4-pyrrolin-2-ones are complimentary to existing procedures and allow for a greater variety of alkylidene substituents.