Michael-TEMPO addition reaction

Scheme 7.8 Domino Michael-TEMPO addition reaction catalysed by chiral amine catalysis and copper catalysis.

More recently, Jang et al. reported a cascade Michael/a-oxyamination reaction of malonates, enals, and a TEMPO-type stable radical by combining iminium catalysis, enamine catalysis, and photoredox catalysis [56], The reaction unified a secondary amine-catalyzed Michael addition of diethyl malonates to enals and a following supported Ru-based photoredox-SOMO catalysis involving a radical trapping event of TEMPO (Scheme 9.61), generating the chiral a, 3-functionalized propanal derivatives with high reactivity and excellent selectivity. 

Jahn combined the formation of the enolate 2-713 resulting from an intermolecu-lar Michael addition of 2-711 and 2-712 with a radical reaction (Scheme 2.157) [363]. The enolate 2-713 did not undergo any further transformations due to the lack of appropriate functionalities. However, after formation of a radical using a mixture of ferrocenium hexafluorophosphate (2-714) and TEMPO, a new reaction channel was opened which afforded the highly substituted cyclopentene 2-715a diastereoselec-tively. 

Moreover, by using only TEMPO without addition of 2-714 the Michael adduct 2-713 is transformed into the isopropenylcyclopentane 2-715b as the major product. The process can also be extended by another radical reaction step [364]. 

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