ChemInform Abstract: ORGANIC PHOTOCHEMISTRY PART 12, THE PHOTODIMERIZATION AND PHOTOISOMERIZATION OF 2‐PYRIDONE AND ITS MONOCHLORO DERIVATIVES

Abstract

Die Bestrahlung des Pyridons (I) in wäßriger Lösung liefert das Dimere (II) und das Valenzisomere (III) in einem von der Konzentration abhängenden Produktverhältnis.

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

“…e. Cycloadditions of 2-Pyridones. Intermolecular photodimerization of 2-pyridones 113 to give stereoisomeric dimers of type 114 and 115 via head-to-head and head-to-tail [4 + 4]-cycloadditions, respectively, is known for quite some time , and constitutes a useful route to cyclooctanoids, Scheme . This theme has been further elaborated by several groups, and many structural variations have been explored.…”

Intramolecular [4 + 4] photocycloaddition of 2-pyridones tethered by a three-carbon chain: studies on the formation of cycloadducts and control of stereogenesis. 3

“…Sharp and Hammond16 demonstrated that a short-lived singlet excited state is responsible for the [4 + 4] reaction, and estimated that the lifetime for this intermediate was less than 200 ps. Several reports have shown that this photodimerization is compatible with chlorine and alkylpyridone substituents, [16][17] with only 6-chloro18 or 4-alkoxy19 substitution unsuitable for the transformation. Only one other study of the intramolecular photochemistry of two pyridones has been reported, Nakamura's triplet-sensitized photoreactions of NJN'polymethylene bis(pyridones) (Figure 1), where the tether constraints combined with photosensitization produced only [2 + 2] and [4 + 2] photoproducts such as 4 and 5.20…”

“…We were also impressed by the absence of reports concerning the chemistry of this photodimerization product, outside of the patented work of Paquette and Slomp at Upjohn. [13][14][15][16][17][18][19][20][21][22] Our initial investigations21 demonstrated that the reaction was compatible with both threeand four-carbon tether lengths. These intramolecular reactions can be run to complete conversion, whereas the intermolecular reaction requires high concentrations (>0.1 M) for [4 + 4] dimerization and unimolecular photoprocesses become significant as concentrations fall below this level.…”

“…These intramolecular reactions can be run to complete conversion, whereas the intermolecular reaction requires high concentrations (>0.1 M) for [4 + 4] dimerization and unimolecular photoprocesses become significant as concentrations fall below this level. [14][15][16][17] The ring formed by the tether removes the inherent symmetry of the photodimerization product 2. We were particularly interested in determining how this asymmetry could be controlled by a center of asymmetry on the tether, analogous to other intramolecular photochemical,23 thermal,24 and radical26 reactions.…”

A new [2 + 2] photodimerization of 5-chloro- and 5-methyl-2-pyridone in their inclusion complexes with 1,1′-biphenyl-2,2′-dicarboxylic acid as a model for DNA damage by photodimerization of its thymine component

“…2 Secondly, photoreaction of 3b and 3c is strongly controlled so as to proceed in the [2 + 2] manner by the crystalline lattice of the inclusion complex. This is also an interesting result, since photoirradiation of 3b in EtOH for 20 h gave the [4 + 4] trans-anti-dimer 8b in 42% yield, 3 and since photoirradiation of 3b in EtOH containing a half molar amount of 5 also gave 8b. Reaction of 3c in solution gave the similar product, 8c.…”