Photoisomerization of 3H -Azepines

Odum, Robert A.; Schmall, Bernard

doi:10.1039/a702465g

Cited by 12 publications

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“…The structures 3 [7], 4 [8], and 5 [ 3 ] obtained here were confirmed by respective comparison with reported data. The regioselectivity of the photoelectrocyclization for 1 was found to be similar to other previously reported 3H-azepines [1].…”

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confidence: 88%

“…One of the typical behavior of cycloheptatriene (CHT) on photo-irradiation is the photoelectrocyclic isomerization giving strained bicyclo[3.2.0]heptadiene ring system. Similarly, photochemical behavior of 3H-azepine has been described by the exclusive formation of 2-azabicyclo[3.2.0]hepta-2,6-diene system v i a bond formation between 4-and 7-position of the ring (4,7-closure) based on the irradiation of 2-alkyloxy-and 2-dialkylamino-3Hazepine derivatives, which were considered to be stabilized azatriene system by iminoether or amidine conjugation [1]. Strangely enough, the other possible bond formation between 2-and 6-position (2,6-closure) giving 6azabicyclo[3.2.0]hepta-2,6-diene system has never been observed (Scheme 1).…”

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confidence: 99%

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Difference in photochemical behavior in 3,6‐ and 2,5‐di‐tert‐butyl‐3H‐azepine: The first photochemical bond formation between 2‐ and 6‐position of 3H‐azepine ring

Satake

Tawada

Takami

et al. 2002

Journal of Heterocyclic Chem

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Different photochemical behavior between 3,6-and 2,5-di-t-butyl-3H-azepine was observed. The former gave wavelength dependent products 3,5-di-t-butylpyridine on irradiation through Pyrex filter via photolysis and 4,7-di-t-butyl-2-azabicyclo[3.2.0]hepta-2,6-diene on irradiation through quartz filter v i a p h o t oisomerization. Meanwhile, 2,5-di-t-butyl derivative gave exclusively a labile 2,5-di-t-butyl-6-azabicyclo-[3.2.0]hepta-2,6-diene on irradiation through Pyrex filter via hitherto unknown photoisomerization mode of the bond formation between 2-and 6-position of the ring. Figure 1. Electronic spectra for 3,6-di-t-butyl-3H-azepine (1), 2,5-di-tbutyl-3H-azepine (6) and cycloheptatriene (CHT) in ethanol.

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Difference in photochemical behavior in 3,6‐ and 2,5‐di‐tert‐butyl‐3H‐azepine: The first photochemical bond formation between 2‐ and 6‐position of 3H‐azepine ring

Satake

Tawada

Takami

et al. 2002

Journal of Heterocyclic Chem

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“…The axiom for the second approach to the preparation of 8 arose from a perusal of earlier literature reports that described rapid photochemical access to 2‐azabicyclo[3.2.0]hept‐6‐en‐3‐one ( 10 ) 35. Irradiation of a solution of 1,3‐dihydro‐2 H ‐azepin‐2‐one ( 9 ; prepared in two steps and 60 % yield from caprolactam,36,37) in Et 2 O for 3 h with a 400 W Hg vapor lamp and a quartz filter provided cycloaddition adduct 10 cleanly in near quantitative yield (Scheme ) 35a,36,38. Without purification, this material was promptly suspended in EtOAc and reduced overnight under H 2 (1 atm) in the presence of 10 % Pd/C.…”

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Crystalline Hetero‐Stereocomplexed Polycarbonates Produced from Amorphous Opposite Enantiomers Having Different Chemical Structures

et al. 2015

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Stereocomplexation is the stereoselective interaction between two opposite enantiomeric polymers through an interlocked orderly assembly. Most studies focus on the stereocomplex formation from the crystalline opposite enantiomers having the identical structure; nevertheless, rare examples were reported regarding the crystalline stereocomplexes from enantiomeric polymers having different chemical structures. Herein we show a strategy for polymer orderly assembly through the formation of crystalline hetero‐stereocomplexed polymeric materials by the cocrystallization of amorphous isotactic polycarbonates with different chemical structures and opposite configurations. The behaviors in the crystalline state are significantly different from that of the component enantiomeric polymers or their homo‐stereocomplexes. This study is expected to open up a new way to prepare various semicrystalline materials having a wide variety of physical properties and degradability.

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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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Photoisomerization of 3H -Azepines

Abstract: Photoelectrocyclization of 3H-azepines substituted in the 2-position with ethoxy, amino, and dimethylamino groups yielded 3-substituted 2-azabicyclo[3.2.0]hepta-2,6-dienes as the only major volatile products, in all cases.

Cited by 12 publications

References 5 publications

Difference in photochemical behavior in 3,6‐ and 2,5‐di‐tert‐butyl‐3H‐azepine: The first photochemical bond formation between 2‐ and 6‐position of 3H‐azepine ring

Difference in photochemical behavior in 3,6‐ and 2,5‐di‐tert‐butyl‐3H‐azepine: The first photochemical bond formation between 2‐ and 6‐position of 3H‐azepine ring

Crystalline Hetero‐Stereocomplexed Polycarbonates Produced from Amorphous Opposite Enantiomers Having Different Chemical Structures

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

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