Oxydative Kupplung von Indolinen und 1,2,3,4‐Tetrahydrochinolinen mit Kaliumpermanganat. 153. Mitteilung über Alkaloide
1974; Wiley; Volume: 57; Issue: 3 Linguagem: Inglês
10.1002/hlca.19740570346
ISSN1522-2675
AutoresHans Jürǵen Rosenkranz, Barbara Winkler‐Lardelli, Hans‐Jürǵen Hansen, H. Schmid,
Tópico(s)Oxidative Organic Chemistry Reactions
ResumoAbstract It is shown that treatment of indolines like 4a‐methyl‐1,2,3,4,4a,9a‐hexahydrocarbazole ( 1 ) and even indoline‐alkaloids like 5 or 6 ( cf. scheme 1 ) with KMnO 4 in boiling acetone solution leads to the indolenines 10, 29 and 33 , respectively, and, in relatively high yields, to N,N′‐ or C,N‐coupling products ( cf. schemes 2 and 5 ). The results of the oxidation of 6‐ or 8‐methoxy‐indolines are shown in schemes 3 and 4 , respectively. Analogous ‘dimeric’ dehydrogenation products are observed when tetrahydroquinolines ( 8 and 9 , resp.) are treated with KMnO 4 ( cf. schemes 7 and 8 , resp.). The formation of the bis‐compounds is almost certainly due to the coupling of two intermediate indolenyl or tetrahydroquinolyl radicals. The cleavage of the hydrazine derivatives 11 or 17 ( scheme 9 ) also leads to ‘dimeric’ C,N‐coupling products. By heating the hydrazine derivative 17 with aqueous HCl, a complete cleavage into indoline 2 and the indolenines 16 and 20 is observed. The reaction is rationalized in scheme 10 . So far no naturally occurring alkaloids related to the above mentioned C,N‐coupling products have been found.
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