A-oxyamination

FIGURE 2.14. Transition state model for the diphenylprolinol trimethylsilyl ether-catalyzed a-oxyamination of aldehydes. 

In 2008, MacMillan and co-workers [13] reported the first total synthesis and structure revision of callipeltoside C (38), a cytotoxic marine macrolide, with amino acid proline as a suitable organocatalyst for the construction of three key intermediates. This elegant synthesis (18 steps, 12% overall yield) demonstrated the power of organocatalysis with unprecedented level of ease and efficiency, which involved a proline-catalyzed double diastereo-differentiating aldol reaction between propionaldehyde 18 and the Roche ester-derived aldehyde 28 to achieve 29 (12 1 dr, 99% ee), an organocatalytic a-oxyamination to afford 32 (99% ee), and proline-... 

Tandem Friedel-Crafts-type allgrlation-a-oxyamination reaction catalysed by chiral resin-supported peptide catalysis and enz5rme catatysis. 

Scheme 5 Merger of photo- and organo-catalysis for a-oxyamination of aldehydes...

More recently, the asymmetric a-oxyamination of aldehydes catalyzed by peptide 29 in combination with oxidative enzyme laccase was reported [44]. This combination promoted the reaction smoothly in water without employing a metal reagent and both the oxyaminated aldehydes and carboxylic acids could be obtained depending on the reaction conditions. 

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. 

Sibi MP, HasegawaM. Organocatalysis in radical chemistry. Enantioselective a-oxyamination of aldehydes. J. Am. Chem. Soc. 2007 129(14) 4124-A125. 

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