摘要:
The ethanolysis rates of 3,3-dimethyl-2-thioxobicyclo[2.2.2]oct-1 triflate and 3,3-dimethyl-2-thioxobicyclo[3.2.2]non-1-yl triflate relative to their corresponding parent compounds (3,3-dimethylbicyclo[2.2.2]oct-1-yl triflate and 3,3-dimethylbicyclo[3.2.2]non-1-yl triflate, respectively) at 25.0 degrees C increase from 10(-6.2) to 10(-2.5). The increase in the rate ratios with the flexibility of the ring system supports the applicability of the authors' methodology to change the conjugative ability of bridgehead carbocations. Formation of 3,3-dimethyl-1,2-epithio-2-ethoxybicyclo[3.2.2]nonane in the ethanolysis of 3,3-dimethyl-2-thioxobicyclo[3.2.2]non-1-yl 2,2,2-trifluoroethanesulfonate indicates cyclization of the intermediate 3,3-dimethyl-2-thioxobicyclo[3.2.2]nonyl cation into an episulfide cation. Computational studies at the HF/6-31G* level indicate that the resonance interaction between the cationic center and the C=S pi system is greater in the 3,3-dimethyl-2-thioxobicyclo[3.2,2]nonyl cation than in the 3,3-dimethyl-2-thioxobicyclo[2.2.2]octyl cation.