Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• achieve optically active α-aminoxy and α-hydroxyamino carbonyl compounds has received considerable attention in the past decades [24]. In 2003, the Yamamoto group demonstrated for the first time that nitrosobenzene could be used as a practical reagent for the catalytic enantioselective α-aminoxylation

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• of the isosteviol moiety could be reduced to the alcohol with NaBH4–EtOH, thus furnishing a second set of modified amphiphilic organocatalysts. These isosteviol-modified hydroxyamino acid organocatalysts were tested with success in asymmetric aldol reactions, α-aminoxylation reactions and three

Continuous proline catalysis via leaching of solid proline

• Suzanne M. Opalka,
• Ashley R. Longstreet and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2011, 7, 1671–1679, doi:10.3762/bjoc.7.197

• ]. Achieving this goal would enable us and others to perform proline-catalyzed reactions, aldol [41][42][43] and Mannich [42] reactions as well as α-functionalizations (α-aminoxylation, α-amination or α-halogenations), continuously [44]. We hypothesized that the proline-catalyzed α-aminoxylation could be

• –proline interactions may also contribute to the rate enhancement [50]. Our group observed that a urea tethered to a tertiary amine increases the rate of a number of batch reactions, including the α-aminoxylation reaction [36][37]. For the α-aminoxylation reaction, we proposed that the urea promotes

• of α-aminoxylation (Scheme 1). It was shown that a longer linker between the urea and amine functionality enhanced the rate of reaction (see Supporting Information of [37]). The rate enhancement enabled the reaction to be performed in greener solvents such as ethyl acetate instead of the more

Continuous-flow enantioselective α-aminoxylation of aldehydes catalyzed by a polystyrene-immobilized hydroxyproline

• Xacobe C. Cambeiro,
• Rafael Martín-Rapún,
• Pedro O. Miranda,
• Sonia Sayalero,
• Esther Alza,
• Patricia Llanes and
• Miquel A. Pericàs

Beilstein J. Org. Chem. 2011, 7, 1486–1493, doi:10.3762/bjoc.7.172

• Franqués, 1. E-08028, Barcelona, Spain 10.3762/bjoc.7.172 Abstract The application of polystyrene-immobilized proline-based catalysts in packed-bed reactors for the continuous-flow, direct, enantioselective α-aminoxylation of aldehydes is described. The system allows the easy preparation of a series of β

• -aminoxy alcohols (after a reductive workup) with excellent optical purity and with an effective catalyst loading of ca. 2.5% (four-fold reduction compared to the batch process) working at residence times of ca. 5 min. Keywords: α-aminoxylation; continuous flow; packed-bed reactors; polystyrene

• organocatalytic approaches to the direct enantioselective α-aminoxylation of carbonyl compounds and, shortly after, to the implementation of the α-aminoxylation of aldehydes with proline as catalyst [14][15] (Scheme 1). In 2004, the scope of the reaction was extended to ketones [16][17] and the reaction was