Isomerisierung und Ringinversion von Tribenzaspiro5.5undecaphanen

摘要

For the two possible ring inversions in tribenzaspiro5.5undecaphanes—corresponding to the isomerizations7→9and9→7resp.—no mutual influence is found. Thus the degenerate isomerizations (“topomerizations”)7→7and9→9can proceedviatwo consecutive (non-concerted) reversals. A ring inversion path similar to that for 2.2metacyclophane (1) is postulated. The considerable ease of the isomerization of9as compared to1can be understood on the basis of thermody