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Rearrangement Reactions in Aza‐Vinylogous Povarov Products: Metal‐Free Synthesis of C 3 ‐Functionalized Quinolines and Studies on their Synthetic Application
Author(s) -
Clerigué José,
Bianchini Giulia,
Ribelles Pascual,
Tejero Tomás,
Merino Pedro,
Ramos M. Teresa,
Menéndez J. Carlos
Publication year - 2019
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.201900986
Subject(s) - chemistry , dehydrogenation , aromatization , intramolecular force , quinoline , alkyl , aryl , reductive elimination , functional group , medicinal chemistry , stereochemistry , organic chemistry , catalysis , polymer
Several types of C 4 ‐functionalized 4‐alkyl‐2‐aryl‐1,2,3,4‐tetrahydroquinolines underwent rearrangement of their functional groups to C 3 , with concomitant aromatization, by simple reflux in 1,2‐dichlorobenzene. The functional groups that were shown to undergo the C 4 to C 3 migration were –CH=CH‐Z (where Z = CO 2 Et, CN, NO 2 , COCH 3 , CH 2 OH) and –CH=C(Y)–Z (where Y = CN and Z = CO 2 Et or Y = Z = CN). On the other hand, the dimethylhydrazono group failed to migrate under thermal conditions but was shown to undergo a smooth dehydrogenation/C 4 to C 3 rearrangement/ dehydrogenation sequence at room temperature in the presence of DDQ, with a broad scope that includes 4‐alkyl‐2‐aryl‐ and 2‐acyl‐1,2,3,4‐tetrahydroquinolines. We also report a computational and experimental study of the mechanism of both reactions, which supports an unusual intramolecular aza‐ene pathway. The ready availability by this method of 2,3‐difunctionalized quinolines allowed the simple preparation of fused heterocyclic systems derived from the pyrrolo[3,4‐ b ]quinoline framework, using both reductive and non‐reductive domino processes.