title: Dienophilic behavior of the vinylic (C=C) and the carbonyl (C=O) bonds of ketenes in reactions with 1,3-diazabuta-1,3-dienes.
abstract: [reaction: see text] Ab initio and density functional studies (DFT) on cycloaddition reactions of 1,3-diazabuta-1,3-dienes with ketenes are reported. The vinylic (C=C) and the carbonyl (C=O) units of the ketenes are found to participate in concerted asynchronous [4 + 2] cycloaddition reactions. The transition states (3t, 4t, and 7t) for these paths have been located on the PE surface at the correlated levels of ab initio calculations. A reasonable mechanism for the formation of [4 + 2] and [2 + 2] adducts is presented.
authors.affiliation: Department of Chemistry and Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar-143005, India.
authors.forename: P V
authors.initials: PV
authors.lastname: Bharatam
authors.forename: R S
authors.initials: RS
authors.lastname: Kumar
authors.forename: M P
authors.initials: MP
authors.lastname: Mahajan