Rearrangement Reactions in Aza‐Vinylogous Povarov Products: Metal‐Free Synthesis of C3‐Functionalized Quinolines and Studies on their Synthetic Application. Issue 38 (12th August 2019)

• Record Type: Journal Article
• Authors: Clerigué, José; Bianchini, Giulia; Ribelles, Pascual; Tejero, Tomás; Merino, Pedro; Ramos, M. Teresa; Menéndez, J. Carlos
• Is Part Of: European journal of organic chemistry. Issue 38(2019)
• Page Start: 6452
• Page End: 6464
• Publication Date: 2019-08-12
• Subjects: Domino reactions -- Nitrogen heterocycles -- Oxidation -- Rearrangement reactions -- Synthetic methods; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201900986
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : 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 = CO2 Et, CN, NO2, COCH3, CH2 OH) and –CH=C(Y)–Z (where Y = CN and Z = CO2 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. Abstract : Highly substituted and functionalized quinolines were obtained by thermal or DDQ‐induced C 4 to C 3 migration of functionalized vinyl substituents in racemic 4, 4‐disubstituted 1, 2, 3, 4‐tetrahydroquinolines.