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Photochemical dehydrogenation, ring contraction, and ring expansion of hydrogenated derivatives of benzoxazino-benzoxazine, quinoxalino-quinoxaline, and bibenzothiazole.

MPS-Authors
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Tauer,  E.
Department of Spectroscopy and Photochemical Kinetics, MPI for biophysical chemistry, Max Planck Society;

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Grellmann,  K. H.
Department of Spectroscopy and Photochemical Kinetics, MPI for biophysical chemistry, Max Planck Society;

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Citation

Tauer, E., & Grellmann, K. H. (1990). Photochemical dehydrogenation, ring contraction, and ring expansion of hydrogenated derivatives of benzoxazino-benzoxazine, quinoxalino-quinoxaline, and bibenzothiazole. Chemische Berichte, 123(5), 1149-1154. doi:10.1002/cber.19901230531.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-0DEA-C
Abstract
The photochemical properties of the title compounds have been investigated and compared. The benzoxazino-benzoxazine derivatives 1 are photochemically converted into hydrogenated oxazole derivatives. In some cases this ring contraction is accompanied by a dehydrogenation reaction whereby the heterocyclic ring system becomes aromatic. Hydrogenated quinoxalino-quinoxalines also undergo a photodehydrogenation reaction and become aromatic. However, a ring contraction yielding the imidazolyl system does not take place. The only investigated sulfur-containing analog has different properties. The stable form is the bibenzothiazole 23 which contains a five-membered heterocyclic ring system. Photochemically 23 rearranges under ring expansion to give the benzothiazino-benzothiazine 24.