Oxidation of hydroxylamines to nitrones catalyzed by (salen)Mn(III) complexes. Enantioselective synthesis of a protected cis-dihydroxypyrroline N-oxide with jacobsen catalyst

Stereocontrolled Cyclic Nitrone Cycloaddition Strategy for the Synthesis of Pyrrolizidine and Indolizidine Alkaloids

“…[23] Enantioselective oxidation of 30 was attempted using a chiral (salen)Mn III catalyst (Jacobsens catalyst) [24] in the presence of a stoichiometric oxidant, to obtain enantioenriched nitrone 31 with up to 36 % ee (Scheme 9). [25] Albeit only moderately enantioselective, the method reported is an interesting rare example of enantiotopic group regioselective discrimination by means of an oxidation reaction.…”

2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides

“…N ‐Oxides are key components for ubiquitously used materials such as toilet soaps, toothpastes, detergents, shampoos, cosmetics, and also found in products for biomedical applications 1. They are also employed as oxidants to accomplish important reactions, such as the osmium‐catalyzed dihydroxylation of olefins,2a the ruthenium‐catalyzed oxidation of alcohols,2b the Mn‐salen‐catalyzed epoxidation of olefins2c and the Pauson–Khand reaction 2d. The most common approach for the synthesis of these compounds is the oxidation of amines (Figure 1) employing stoichiometric amounts of peracids,3a,b activated H 2 O 2 ,3c dioxiranes3d–f or oxaziridines 3g.…”

Enantiopure Cyclic Nitrones: A Useful Class of Building Blocks for Asymmetric Syntheses

“…The Jacobsen catalyst was used to discriminate enantiotopic hydrogen atoms in the oxidation of meso Nhydroxypyrrolidine 57 with a variety of oxidants, including urea hydrogen peroxide, sodium hypochlorite, iodosylbenzene and the m-chloroperbenzoic acid/N-methylmorpholine N-oxide system. 44 A mixture of enantiomeric nitrones 58 and (ent)-58, variably enriched in the enantiomer (2R,3S)-58 depending on the oxidant, was obtained (Scheme 14). Although the asymmetric induction was modest, this work is the only example of an asymmetric oxidation of hydroxylamines.…”

“…Although the asymmetric induction was modest, this work is the only example of an asymmetric oxidation of hydroxylamines. 44…”