Reaction of (Aminocarbene)iron Complexes with Alkynes. A Synthesis of 5-Aminofurans

Alkynes react with ((dimethyiamino)phenyl-methylidene)tetracarbonyliron(0), compound 3, with incorporation of CO to give 5-(dimethylamino)furans as the major products. Consistent with the mechanism proposed here and related to the mechanism proposed earlier for reactions of the corresponding (alkoxy-alkylidene)iron complexes, the product distribution is CO-pressure-dependent, producing 6-(dimethylamino)-α-pyrones at the expense of furans under higher CO pressure. The regioselectivity in the addition of alkynes parallels that observed in the reactions of alkynes with (alk-oxyalkylidene)chromium and -iron analogues. The 5-(di-methyiamino)furans are relatively little studied; high reactivity toward oxygen and maleic anhydride is observed.