Transition Metal Complexes of Diazenes, XL [1] Iron Carbonyl Assisted Formation of Bicyclic 1,2-Dihydropyrazol-3-ones from Pyrazolines and Alkynes

Abstract

The oxidative degradation of a tricyclic dicarbonyl iron complex substituted at the diazaferrole ring by ester groups ( 1b ) does not lead to a bicyclic 1,2,3-diazepinone derivative, as reported recently for the case of the phenyl substituted compound (1a ), but affords the bicyclic 4-stilbenyl-1,2-dihydropyrazol-3-one 2b as shown by X-ray structural analysis. Since 1b is obtained by reaction of two different alkynes with a hexacarbonyldiiron complex of the cyclic 1,2-diazene, the over-all reaction formally consists of the addition of CO and two alkyne molecules to an N = N function affording a vinyl substituted diazacyclopentenone ring, and may be viewed as a type of hetero Pauson-Khand reaction.