Equilibrium Acidities of Nitroalkanes in an Ionic Liquid
The acidity ladder scale in [BMPY][NTf2] was successfully expanded toward the weak acidity region for about five more pK units compared to the previously established one. This allows the acidities of a series of 13 aliphatic and aromatic nitroalkanes to be determined accurately by the UV-vis spectroscopic method. The acidity of nitroalkane in [BMPY][NTf2] covers ~8 pK units and is significantly weaker than those in DMSO and water. The Hammett plot for 4-substituted phenylnitromethanes shows an excellent linearity with a slope of 2.06, which is rather close to that in DMSO but significantly larger than that in water (0.80). The regression analyses reveal that the solvation behavior of [BMPY][NTf2] on the acidic dissociations of C-H acids is similar to that of DMSO.
Thermal ring enlargement of aromatic cyclopentadienylidene iminyl radicals. Intramolecular radical addition to the N atom of nitriles results in high yields of aza-aromatics
It has been demonstrated that ketiminyl radicals, formed at high temperatures (1000 °C, 0.3 s) in oxygen-free nitrogen from phenylhydrazones of benz-anellated cyclopentadienones (fluorenone (9a), methanophenanthrenone (9b)), yield into phenanthridine (8a) and benzo[lmn]-phenanthridine (8b) in yields > 60%. The results point to a predominant addition of intermediately generated phenyl type radicals 5 to the N atom of the nitrile groups followed by bimolecular H-abstraction of the cyclic imidoyl radicals to 8.
Hofmann, Joerg,Schulz, Kathrin,Zimmermann, Gerhard
p. 2399 - 2402
(2007/10/03)
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