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Efficient Synthesis of Maxonine Analogues from N ‐Substituted Benzyl‐1‐formyl‐9 H ‐β‐carbolines
Author(s) -
Hutait Samiran,
Biswas Subhasish,
Batra Sanjay
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200068
Subject(s) - chemistry , moiety , aldehyde , intramolecular force , acetal , ring (chemistry) , stereochemistry , protonation , yield (engineering) , medicinal chemistry , adduct , catalysis , organic chemistry , ion , materials science , metallurgy
Acid‐catalyzed Pomeranz–Fritsch‐type reaction between the acetal group at C‐1 and the arene unit of the benzyl group at N‐9 in 9‐substituted benzyl‐1‐(dimethoxymethyl)‐9 H ‐β‐carboline affords fused‐β‐carbolines that can be readily oxidized to furnish a maxonine‐type framework. Mechanistically, the reaction proceeds via a protonated aldehyde as the intermediate, which undergoes attack by the activated arene subunit of the benzyl moiety. On the other hand, the Morita–Baylis–Hillman adducts of 1‐formyl‐ N ‐substituted benzyl‐9 H ‐β‐carbolines undergo an efficient P 2 O 5 ‐mediated intramolecular Friedel–Crafts reaction between the secondary hydroxy group and the activated phenyl group of the benzyl subunit to yield fused‐β‐carbolines. Investigations into the scope of the substrates reveal that the success of the methodology relies on the degree of activation of the phenyl ring. For substrates having less‐activated phenyl groups, indolizinoindole derivatives were isolated in moderate yields only.