Irradiation of 3,4,5-trideuteriopyridine at 254 nm in the vapor phase results in the formation of a mixture of 2,3,4-trideuteriopyridine and 2,3,6-trideuteriopyridine. The formation of these products is consistent with a photoisomerization mechanism involving equilibrating azaprefulvene intermediates. This is the first direct evidence that pyridine vapor undergoes photoisomerization resulting in transposition of the pyridine ring atoms. (C) 2003 Elsevier Ltd. All rights reserved.
Synthesis and spectroscopic properties of isomeric trideuterio- and tetradeuterio pyridines
作者:James W. Pavlik、Somchoke Laohhasurayotin
DOI:10.1002/jhet.5570440637
日期:2007.11
The syntheses of the six possible isomeric trideuteriopyridines and the three possible isomeric tetradeuteriopyridines are described. These deuteriopyridines were characterized by their mass and NMR spectra.
Deuterodecarboxylation, the replacement of a COOD group by a D atom, proceeds with high specificity in good yields for a series of pyridine-2-carboxylic acids. Isomeric pyridine-carboxylic acids require higher temperatures to achieve decarboxylation and give multiply deuterated products. Positions adjacent to the ring N are especially favored in the H—D exchange reactions. The role of ylid intermediates
The Vapor-Phase Phototransposition Chemistry of Pyridine: Deuterium Labeling Studies
作者:James W. Pavlik、Somchoke Laohhasurayotin
DOI:10.1021/jo7026799
日期:2008.4.1
The six isomeric trideuteriopyridines and the three isomeric tetradeuteriopyridines undergo phototransposition upon S0 → S2 (π, π*) excitation in the vapor phase at 254 nm. On the basis of the products formed, the six trideuteriopyridine isomers can be divided into two triads. Similarly, the three isomeric tetradeuteriopyridines also constitute a triad. Irradiation of any one member of each triad results