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Conformation in solution of tetraaryl‐3,7‐diazabicyclo[3.3.1]‐nonanes and tetra‐ and pentaaryl‐1,3‐diazaadamantanes. A nuclear magnetic resonance study
Author(s) -
Jackman Lloyd M.,
Dunne Theresa S.,
Müller Bodo,
Quast Helmut
Publication year - 1982
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19821150818
Subject(s) - chemistry , cyclohexane conformation , aryl , crystallography , tetra , molecule , nuclear magnetic resonance spectroscopy , stereochemistry , chemical shift , nuclear overhauser effect , proton nmr , nuclear magnetic resonance , hydrogen bond , medicinal chemistry , organic chemistry , alkyl , physics
The proton NMR spectra of a series of tetraaryl‐3,7‐diazabicyclo[3.3.1]nonanes, 5 – 12 , have been assigned with the aid of nuclear Overhauser difference spectroscopy. The NOE's together with spin lattice relaxation times have been used to show that these molecules adopt the chair‐boat conformation with all aryl groups being equatorial. This conformation and the torsional angles of the aryl groups are similar to those found in the solid state. Analogous studies have been carried out with tetra‐ and pentaaryl‐1,3‐diazaadamantanes, 3 , 4 , 13 , and 14 . A surprisingly low barrier of rotation ( 4b : δ G 298 ≠= 42 kJ. mol −1 ) has been found for the two 1,3‐diaxially oriented aryl groups in these systems. Carbon‐13 chemical shift data are reported for the above compounds. Those of the 3,7‐diazabicyclononanes 5 – 12 are found to be consistent with the proposed chair‐boat conformation. Nitrogen‐15 chemical shift data and 13 C‐ 15 N coupling constants are also in accord with this conformation. A stereoselective reduction of 4,8,9,10‐tetrakis(3,5‐dimethylphenyl)‐1,3‐diaza‐6‐adamantanone ( 4b ) to the corresponding alcohol 15 and the ready acidcatalyzed rearrangement of this alcohol to 16 , the first example of the 9‐oxa‐1,5‐diazatricyclo‐[5.3.1.0 3,8 ]undecane ring system, is described.