Enantioselective Construction of Octahydroquinolines via Trienamine-Mediated Diels–Alder Reactions

Abstract

A trienamine-mediated asymmetric Diels− Alder reaction using a 5-nitro-2,3-dihydro-4-pyridone derivative as a dienophile in the presence of a secondary amine organocatalyst derived from cis-hydroxyproline was discovered. The reaction provides optically active octahydroquinolines through an endo-selective [4 + 2] cyclization pathway. The following stereoselective denitration, isomerization, and/ or hydrogenation generated divergent stereoisomers of decahydroquinolines, which are useful synthons for the total synthesis of Lycopodium alkaloids. Letter pubs.acs.org/OrgLett

Trisubstituted push-pull nitro alkenes

“…Resulting N,Ndimethylamino nitroalkene contains a relatively good leaving group which may facilitate further nucleophilic reactions (Scheme 4). This method was mostly exploited for the preparation of reviewed structures with acyl group 18,[42][43][44][45] as the second electron-withdrawing group.…”

Polyenals and Polyenones in Aminocatalysis: A Decade Building Complex Frameworks from Simple Blocks

“…In 2019, Ishikawa et al used the 5‐nitro‐2,3‐dihydropyridone 26 as dienophile to react with 2,4‐dienals 25 by applying trienamine catalyzed endo selective [4+2] cycloaddition reaction to construct octahydroquinoline derivatives 27 with moderate to high yields and excellent enantioselectivities (Scheme ) …”

DMAP Catalyzed Domino Rauhut–Currier Cyclization Reaction between Alkylidene Pyrazolones and Nitro-olefins: Access to Tetrahydropyrano[2,3-c]pyrazoles

“…This resulted in the formation of an amine which was protected with benzoyl chloride to provide 4 in 92% yield with preservation of diastereoselectivity. Then 3aa was treated with catalytic 2,2′-azobisisobutyronitrile (AIBN) and 1 equiv of n -Bu 3 SnH for radical denitration . The disubstituted tetrahydropyrano­[2,3- c ]­pyrazole 5 was obtained in 70% yield, and here also, no erosion in diastereoselectivity was detected.…”