Microwave-Assisted Reactivity of a Fischer Alkynyl Carbene Complex with Benzylidene Anilines

The reaction between the Fischer carbene complex (CO)5Cr=C(OEt)C equivalent to CPh and various benzylidene anilines RCH=NR1 was promoted by microwave irradiation, generating stable cross-conjugated metallahexatrienes in 45-70 % yield. Compared to conventional heating, the present conditions provided shorter reaction times with moderate yields. The geometrical configuration and the most stable conformation for each of the Fischer carbene complexes and their oxidation products were established by NMR and DFT analysis. The reaction mechanism was explored by DFT calculations of the potential energy surface, suggesting a 1,4-addition/ring closure/electrocyclic opening cascade process.