Armstrong, D.R. and Henderson, Kenneth. W. and MacGregor, M. and Mulvey, Robert and Ross, M.J and Clegg, W. and O'Neil, P.A. (1995) Synthetic and theoretical MO calculational studies of lithiotriazine intermediates produced during alkyllithium-induced cyclotrimerisation reactions of organic nitriles, and comparison of their structures with that of a methylmagnesiotriazine derivative. Journal of Organometallic Chemistry, 486 (1-2). pp. 79-93. ISSN 0022-328XFull text not available in this repository. (Request a copy from the Strathclyde author)
Benzonitrile can be readily cyclotrimerised by treatment with a suitable alkyllithium to give a simple triazine, or to a solvated lithiodihydrotriazine derivative. Which cyclic product dominates depends mainly on the source of the active Li+ cation (n-butyllithium, t-butyllithium and tetramethylguanidinolithium are considered here), and on the solvent employed. X-ray crystallographic studies on a representative compound show that the lithio species exists as a mononuclear, contact ion pair structure, with the triazine ring in a 1,4-dihydro state. On reaction with the Grignard reagent, MeMgCl, this compound gives a methylmagnesiodihydrotriazine, which has also been crystallographically characterised and found to closely resemble its lithio precursor. Ab initio MO calculations on model systems reveal that the 1,4-dihydrotriazine arrangement is energetically preferred to the 1,2-dihydro alternative irrespective of the counterion (Li+ or H+) present. A theoretical investigation of the methanolysis of the lithio species indicates that the formation of an intermediate MeOH complex, with the alcohol attached to a ring N atom and not to Li+, directs the reaction towards ultimate formation of a 1,2-dihydrotriazine.
|Keywords:||triazine, lithium, magnesium, Ab initio, crystal structure, organomagnesium compounds, lithium compunds, ring stacking, Chemistry, Materials Chemistry, Biochemistry, Organic Chemistry, Physical and Theoretical Chemistry, Inorganic Chemistry|
|Subjects:||Science > Chemistry|
|Department:||Faculty of Science > Pure and Applied Chemistry|
|Depositing user:||Pure Administrator|
|Date Deposited:||05 Mar 2012 16:28|
|Last modified:||05 May 2016 00:20|