AI Article Synopsis
- The NMR spectra of imines and nitrones derived from benzophenone and phenylalanine or tyrosine indicate an aromatic edge-to-face interaction in solution, especially noted at low temperatures.
- The ortho protons of the phenyl ring involved in CH-pi interactions show a significant upfield shift, with the affected signal appearing at delta 5.4-5.8 at -88 degrees C, while the introduction of a para substituent slightly influences this shift.
- Additionally, edge-to-face interactions are also evidenced in the X-ray crystal structures of the compounds, and barriers to rotation around the syn phenyl-imino bond are measured between 10.5-11.1 kcal mol(-1).
Article Abstract
NMR spectra of imines and nitrones derived from benzophenone and phenylalanine or tyrosine show clear evidence of an aromatic edge-to-face interaction in solution. At low temperatures the two ortho protons of the edge interacting phenyl ring become topically resolved with the ortho proton NMR signal involved in the CH-pi interactions shifted well upfield (delta 5.4-5.8 at -88 degrees C) of the other ortho signal. Introduction of a para substituent into the phenylalanine ring has a modest effect on the upfield shift. The edge-to-face arrangement also manifests in the X-ray crystal structures of two of these compounds. Barriers to rotation around the syn phenyl-imino bond are also reported (10.5-11.1 kcal mol(-1)).
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| http://dx.doi.org/10.1039/b916021n | DOI Listing |
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