The Search for Homoaromatic Semibullvalenes. 5.<sup>1</sup> 1,5-Dimethyl-2,4,6,8-semibullvalenetetracarboxylic Dianhydride
作者:Richard Vaughan Williams、Vijay R. Gadgil、Kamlesh Chauhan、Lloyd M. Jackman、Errol Fernandes
DOI:10.1021/jo972010x
日期:1998.5.1
The synthesis and study of a novel bisannelated semibullvalene that is calculated to be a neutral homoaromatic ground state molecule is presented. Through variable-temperature X-ray, C-13 solution-phase NMR, and C-13 solid-state CP-MAS NMR studies and by a modified Saunders' isotopic perturbation method, 1,5-dimethyl-2,4,6,8-semibullvalenetetracarboxylic dianhydride is shown to be a highly fluxional molecule that is not homoaromatic in the solution or solid states, The barrier to the Cope rearrangement of this dianhydride, in solution, is estimated (from 125 MHz C-13 NMR data) to be less than 14 kJ mol(-1).