Cu(TFA)₂-Catalyzed Oxidative Tandem Cyclization/1,2-Alkyl Migration of Enamino Amides for Synthesis of Pyrrolin-4-ones

Abstract

A novel Cu(TFA)2-catalyzed oxidative tandem cyclization/1,2-alkyl migration of readily available enamino amides for the synthesis of pyrrolin-4-ones has been developed. The reaction tolerates a wide range of functional groups and is a reliable method for the rapid synthesis of substituted pyrrolin-4-ones in high yields under mild conditions.

Synthesis of Polycarbonyl Pyrroles via K2S2O8-Mediated Oxidative Cyclization of Enamines

“…A control experiment in which 2 equiv of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) or 2,6-di- tert -butyl-4-methylphenol (BHT) was added to the model reaction failed to afford the pyrrole product 2a , suggesting that the reaction may involve a radical process. On the basis of our experimental results and the literature, , a possible mechanism is proposed (Scheme ). Initially, oxidation of enamine 1 by K 2 S 2 O 8 generates amino radical cation A , which reacts with a second molecule of enamine 1 to form intermediate B .…”

Copper(II)‐Mediated Intermolecular Radical [3+2]‐Annulation of N,N‐Dimethyl Enaminones: Direct Access to 5‐Acyl‐3‐Furancarboxaldehydes

“…On the basis of the above experimental results, a tentative mechanism of this intermolecular radical transformation of N , N ‐dimethyl enaminones is proposed in Scheme 5. Initially, N , N ‐dimethyl enaminones 1 is oxidized by Cu(II) to generate the radical cation intermediate 11 , which can further tautomerize to produce the corresponding carbon centered radical intermediate 12 [11a,f] . Subsequently, the radical addition of 12 across a C=C bond in another molecule of N , N ‐dimethyl enaminones 1 generates the radical intermediate 13 , followed by 5‐ endo ‐trig radical cyclization with the carbonyl oxygen to afford the radical intermediate 14 .…”

Recent development in the synthesis of pyrrolin‐4‐ones/pyrrolin‐3‐ones

“…Enamino amides with a variety of substituents such as methyl, methoxyl, fluoro, chloro, bromo, iodo, and strong electron‐withdrawing groups such as cyano, acetyl, and ester provide corresponding substituted pyrrolin‐4‐ones 64 in good to high yields (Scheme 19). 17 …”