Studies of novel synthesis of functionalized polycyclic ring systems through the coupling reactions of Fischer carbene chromium complexes with enyne hydrazones and aldehydes

The main focus of this research has been exploring the novel synthesis of functionalized polycyclic ring systems through the coupling reactions of Fischer carbene complexes with enyne hydrazones and aldehydes. To this effect three major types of reactions involving Fischer carbene chromium complexes have been studied in detail. Three component coupling reactions of carbene chromium complexes with a variety of dienyn hydrazones and electron deficient dienophiles have been explored in detail. The major intermediate of the reaction between alkynylindolehydrazone system and methylmethoxy carbene chromium complex has been isolated and characterized. Alkynyl N,N-dimethylhydrazones of thiophene, furan and pyrrole systems, have been subjected to the three component coupling reaction with methylmethoxy carbene chromium complexes to yield aromatic polycyclic products. Hydrazone derivatives of ortho-alkynylbenzaldehydes with N-phenyl, N-methyl hydrazenes have been prepared and employed in three component coupling reactions. Dihydrooxazole derivatives of different ring sizes have been prepared and subjected to the three component coupling reactions to investigate scope and limitations of the procedure.;A novel CO insertion reaction involving methoxyalkynylphenyl chromium carbene complexes and dienyne carboxaldehydes has been explored and two possible mechanisms for the CO inserted product formation have been evaluated. This methodology has been extended to aromatic and non-aromatic carboxaldehyde substrates as well as to aromatic and non-aromatic methoxyalkynyl carbene complexes. Depending on in depth analysis of the product formation and distribution a mechanism has been presented as the most reasonable pathway to explain the observed product formation.;Coupling of reactions of gamma,delta-unsaturated carbene chromium complexes with electronically different substrates have been investigated to ascertain the electronic effect on the product distribution in [5+5] cycloaddition reactions.