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Quinoline synthesis: scope and regiochemistry of photocyclisation of substituted benzylidenecyclopentanone O-alkyl and O-acetyloximes
Austin, Mark; Egan, Oliver James; Tully, Ray; Pratt, Albert C.
Irradiation of substituted 2-benzylidenecyclopentanone O-alkyl and O-acetyloximes in methanol provides a convenient synthesis of alkyl, alkoxy, hydroxy, acetoxy, amino, dimethylamino and benzo substituted annulated quinolines. para-Substituents yield 6-substituted-2,3-dihydro-1H-cyclopenta[b]quinolines with 8-substituted products being obtained from ortho-substituted starting materials. Reactions of meta-substituted precursors are highly regioselective, with alkyl substituents leading to 5-substituted 2,3-dihydro-1H-cyclopenta[b]quinolines and more strongly electron-donating substituents generally resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo- and thieno-[2,3e]pyridines respectively. Sequential E- to Z-benzylidene group isomerisation and six [pi]-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone O-allyloxime, singlet excited states are involved in both steps.
Keyword(s): Organic chemistry; Chemistry
Publication Date:
2007
Type: Other
Peer-Reviewed: Unknown
Language(s): English
Institution: Dublin City University
Citation(s): Austin, Mark, Egan, Oliver James, Tully, Ray and Pratt, Albert C. (2007) Quinoline synthesis: scope and regiochemistry of photocyclisation of substituted benzylidenecyclopentanone O-alkyl and O-acetyloximes. Organic and Biomolecular Chemistry, 5 (23). pp. 3778-3786. ISSN 1477-0520
Publisher(s): Royal Society of Chemistry
File Format(s): application/pdf; image/gif
Related Link(s): http://doras.dcu.ie/119/1/obc_2007_author_copy.pdf,
http://doras.dcu.ie/119/2/obc_2007_supp_info.pdf,
http://doras.dcu.ie/119/3/abstract_image.gif,
http://dx.doi.org/10.1039/b711620a
First Indexed: 2009-11-05 02:00:16 Last Updated: 2019-02-09 07:05:24