- Anomalous substituent effects in the Bischler-Napieralski reaction of 2-aryl aromatic formamides
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Treatment of some 1-naphthylformamides (or formanilides) possessing a 2,4,5-trioxygenated phenyl substituent at the 2-position with POCl3 caused an unprecedented carbon insertion reaction into a benzene ring, producing 7-5 ring (azaazulene) systems as valence isomers of isoquinoline skeletons. Precise examination of this abnormal Bischler-Napieralski reaction (BNR) using various substrates led to the following scope and limitations: (i) the 7-5 ring systems were constructed when either 2-alkoxy-4,5-methylenedioxyphenyl- or 4,5-dialkoxy-2-hydroxyphenyl-substituted formamides were used as a starting substrate; (ii) in the former case the formyl carbon was inserted into the C1-C6 bond of the 2-phenyl group, and normal isoquinoline cyclization competed with an abnormal carbon insertion reaction; (iii) the presence of a hydroxy group at the 2′-position as in the latter cases caused exclusive carbon insertion, in which alternative C1-C2 insertion products were quantitatively formed; (iv) 3,6-dimethoxy-2-hydroxyphenyl-substituted formanilide electronically equivalent to 4,5-dialkoxy-2-hydroxy derivatives produced an indole-pyrone as an abnormal BNR product. Theoretical approaches using the PM-3 method indicated that these abnormal BNRs could be triggered by ipso attack at the 1′-position yielding spiro intermediates. Ring cleavege of the six-membered ring in the spiro intermediates to a ketene function followed by recyclization was proposed for the 2′-hydroxy-directed abnormal BNRs leading to the C1-C2 insertion product or the indole-pyrone derivative.
- Ishikawa,Shimooka,Narioka,Noguchi,Saito,Ishikawa,Yamazaki,Harayama,Seki,Yamaguchi
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p. 9143 - 9151
(2007/10/03)
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- Baeyer-Villiger-type Oxidation of an Immonium Group: The Structural Establishment of Naturally Occurring Amides Related to Benzophenanthridine Alkaloids
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Structures of four new amide-alkaloids, arnottianamide (1), isoarnottianamide (2), integriamide (3), and iwamide (4), which occur naturally in Xanthoxylum plants, were established by derivation from the known benzophenanthridine alkaloids chelerythrine (5), nitidine (6), avicine (7), and decarine (8).In these transformations, the novel Baeyer-Villiger-type oxidation of an immonium group was applied.
- Ishii, Hisashi,Ishikawa, Tsutomu,Lu, Sheng-Teh,Chen, Ih-Sheng
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p. 1769 - 1774
(2007/10/02)
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