Conformational isomers in the photocyclodimerization of N-acylated dibenz[b,f]azepine derivatives

Querner, Jens; Scheller, D.; Wolff, Thomas

doi:10.1016/s1010-6030(02)00034-5

Cited by 7 publications

(12 citation statements)

References 11 publications

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“…The N-alkyl DBA 2±7 slowly produce high molecular-weight products, clearly distinct from photodimers and acridines, which were not investigated in detail. Similar to the photodimers of 10 and 14, [5] those of 9, 16, 19, 20, and 21 exist in two rotameric forms, that is, in Z and E configurations with respect to the amide groups, which result from the restricted rotation of the C±N of the amide bond, see Scheme 2. According to a previous study, [5] the Z and E rotamers can be best distinguished from the 1 H NMR signals of the cyclobutane protons.…”

Section: Continuous Sensitized Irradiationmentioning

confidence: 80%

“…Similar to the photodimers of 10 and 14, [5] those of 9, 16, 19, 20, and 21 exist in two rotameric forms, that is, in Z and E configurations with respect to the amide groups, which result from the restricted rotation of the C±N of the amide bond, see Scheme 2. According to a previous study, [5] the Z and E rotamers can be best distinguished from the 1 H NMR signals of the cyclobutane protons. Table 4 gives the fractions of Z and E conformers which were obtained from integrals of the NMR signals after photodimerization and dissolving the dimer in the NMR solvent.…”

Section: Continuous Sensitized Irradiationmentioning

confidence: 80%

“…[5] In these and all other photodimers, the anti-configuration was concluded from the coupling pattern of the cyclobutane protons in the 1 H NMR spectra. For 9, 16, 19±21 two AA'BB' spin systems were found in the 1 H NMR spectra of the cyclobutane protons.…”

Section: Characterization Of Photodimersmentioning

confidence: 87%

“…It was concluded that the reaction proceeds through the triplet state of the DBA thereby differing from other stilbenes which undergo dimerization upon direct irradiation, that is, through the singlet excited state. [3,4] Moreover, only N-acyl derivatives, such as N-acetyl (10) and N-propionyl DBA (14) [1, 2,5] or the pharmaceutically active N-carbamoyl compound ™carbamazepine∫ (21), were found to photodimerize.…”

Section: Introductionmentioning

confidence: 99%

“…[7] Upon photodimerization the cyclobutane ring was formed exclusively in the anti-configuration; [8±10] in solution isomeric dimers differing in the amide bond configuration were detected for 10 and 14. [5] For the non-substituted dibenzazepine (1) and its N-acetyl (10) and N-valeroyl (15) derivatives, low quantum yields of intersystem crossing (F ISC ) were reported. [11] For benzophenone-sensitized excitation of 15, an anti-cyclobutane dimer is formed with a quantum yield of photodimerization of up to F d = 0.15.…”

Section: Introductionmentioning

confidence: 99%

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Substituent‐Dependent Reactivity in the Photodimerization of N‐Substituted Dibenz[b,f]azepines

Querner

Wolff

Görner

2003

Chemistry A European J

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The photoprocesses of a series of N-substituted dibenz[b,f]azepines (iminostilbenes) were studied by absorption and emission spectroscopy, by laser flash photolysis, and by preparative irradiation with NMR analysis. In solutions, 2pi+2pi photodimers of N-cyano and N-acyl dibenzazepines are formed via the triplet state upon acetone- or benzophenone-sensitized energy transfer. T-T absorption spectra were measured and absorption coefficients were determined. The triplet energy transfer is equally efficient for N-alkyl dibenzazepines, which do not dimerize. Excited states of npi* character in the latter cases are discussed to rationalize the different reactivities. In spite of negligible intersystem crossing of 21 dibenzazepine derivatives, photodimers of N-acyl and N-cyano dibenzazepines are formed upon direct excitation in concentrated solutions (0.01-0.1 mol dm(-3)) as well as in the solid state. A selective anti-configuration of the photodimers was found throughout.

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Section: Continuous Sensitized Irradiationmentioning

confidence: 80%

Section: Continuous Sensitized Irradiationmentioning

confidence: 80%

Section: Characterization Of Photodimersmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Substituent‐Dependent Reactivity in the Photodimerization of N‐Substituted Dibenz[b,f]azepines

Querner

Wolff

Görner

2003

Chemistry A European J

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NMR Spectroscopy of Cyclobutanes

Seidl

Dias

2009

Patai's Chemistry of Functional Groups

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Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Vaquero

Cuadro

Herradón

2011

Modern Heterocyclic Chemistry

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The replacement of a carbon atom by a heteroatom in a seven-membered carbocycle leads to the corresponding seven-membered heterocyclic ring system. Different types of heterocycles can be formed depending on the nature of the carbocycle. In a cycloheptatriene the replacement can involve any of the six sp 2 hybridized carbons or the sp 3 carbon atom, whereas in cycloheptane all carbon atoms are equivalent and replacement affords exclusively the fully saturated heterocyclic systems. Partially saturated seven-membered heterocycles can be viewed as derivatives or related systems of these two main seven-membered heterocyclic units arising from carbon replacement in cycloheptatriene and in cycloheptane. Replacement of the sp 3 hybridized carbon atom in cycloheptatriene by a nitrogen leads to an azacycloheptatriene known as 1H-azepine (1) and the corresponding 2H-, 3H-, and 4H-azepines (2-4) are the tautomeric forms generated by the replacement of the sp 2 carbons. 1H-Azepine is an unstable red oil that is prone to rearrange to the also unstable 3H-azepine in the presence of acids and bases. However, this tautomer seems to be more stable than both 4H-and 2H-azepine. The structures related to 1H-azepine that bear an oxygen or sulfur atom are known as oxepine (5) and thiepine (6) (thiepin is favored by Chemical Abstracts Service). Oxepine is much more stable than thiepine and has been synthesized, isolated, and characterized at room temperature while thiepine has not been detected to date. Stable monocyclic thiepines were prepared and characterized in the 1980s. Azepines, oxepines, and thiepines that are constrained to planar or almost planar conformations should be antiaromatic molecules with negative resonance energy and, as a consequence, these compounds are unknown.The fully saturated seven-membered heterocycle containing one nitrogen is azepane (7) (hexahydroazepine or perhydroazepine); the oxygen and sulfur analogues are known as oxepane (8) and thiepane (9). All of these compounds are stable and show typical behavior of secondary amine, ether and thioether, respectively. TwoModern Heterocyclic Chemistry, First Edition. Edited

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Conformational isomers in the photocyclodimerization of N-acylated dibenz[b,f]azepine derivatives

Cited by 7 publications

References 11 publications

Substituent‐Dependent Reactivity in the Photodimerization of N‐Substituted Dibenz[b,f]azepines

Substituent‐Dependent Reactivity in the Photodimerization of N‐Substituted Dibenz[b,f]azepines

NMR Spectroscopy of Cyclobutanes

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

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