- Rotation in biphenyls with a single ortho-substituent
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Barriers to rotation in a range up to 15.4 kcal mol-1 were determined by dynamic NMR spectroscopy for a series of biphenyl compounds 1a-1h and 2a-2d with a single ortho-substituent. Ab initio calculations reproduce these barriers satisfactorily
- Mazzanti, Andrea,Lunazzi, Lodovico,Minzoni, Mirko,Anderson, J. Edgar
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p. 5474 - 5481
(2007/10/03)
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- Fascinating problems in organic reaction mechanisms-VI. Bromonitrocamphane anhydrobromonitrocamphane rearrangement
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The fascinating bromonitrocamphane(1)→anhydrobromonitrocamphane(2) change has been examined in detail. The structure of 2 has been confirmed by X-ray analysis and other physical data. The 1 → 2 transformation belongs to the rather uncommon fragmentation-rearrangement-recombination pathway and the three distinct stages involved, namely, the loss of the nitro group, the rearrangement of the bornane cation so generated to 4-bromocamphene(3) and the subsequent reacceptance of elements of the lost nitro group, have been confirmed on basis of experimental data, particularly employing 15N sodium nitrite. The remarkable bromonitrocamphane(1)→4-bromotricyclene acid(8) change, the useful camphene→9 transformation and the amusing 15→16 change have been discovered. The concerted nature of the camphene→11 reaction has been established with optically active camphene and this study has helped in identifying the stage where optical activity is lost in the 1 → 2 change. Kinetic studies have shown that in the highly strained tricyclic isoxazolines 11, 2 and 16, the 4-substituents, through inductive effect, greatly affect the stability of the isoxazoline ring. The facile rupture of such isoxazolines have provided an efficient route to doubly functionalized bornanes.
- Ranganathan,Raman
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