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

• . Keywords: aminoxylation; flow chemistry; heterogeneous catalysis; packed-bed microreactor; proline/thiourea catalysis; Introduction Continuous flow chemistry [1][2][3], performed in small dimension tubing or channels, differs from batch chemistry in that mixing and heat transfer are significantly faster

• ]. 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

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

• chiral enantiopure Lewis acids as catalysts [6][7][8][9][10][11]. Worth noting is the contribution made by Yamamoto et al., who introduced the use of nitrosobenzene as an electrophilic source of oxygen in the aminoxylation of preformed tin enolates catalyzed by a chiral, silver-based Lewis acid [12