Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors

• Ming-Liang Zhang,
• Deng-Feng Yue,
• Zhen-Hua Wang,
• Yuan Luo,
• Xiao-Ying Xu,
• Xiao-Mei Zhang and
• Wei-Cheng Yuan

Beilstein J. Org. Chem. 2016, 12, 295–300, doi:10.3762/bjoc.12.31

• successfully used as chiral organocatalysts for the asymmetric Michael addition and Mannich reactions [12][13][14]. Meanwhile, the Henry reaction is one of the most important carbon–carbon bond-forming reactions that provides straightforward access to β-nitroalcohols, which can be further transformed into

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

• ]. The amphiphilic organocatalysts, often referred to as hydroxyamino acid (serine or threonine) surfactant organocatalysts by the authors, were then applied with success in asymmetric anti-Mannich reactions and asymmetric aldol reactions of ketones and aromatic aldehydes, in the presence of water [54

• -component Mannich reactions under aqueous conditions [65][66][67]. Use of chemoselective O-acylation of hydroxyproline for preparation of polymeric organocatalysts The last couple of years have witnessed an interesting proliferation in the use of chemoselective O-acylation of hydroxyproline with acrylic

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

• catalyst for the direct enantioselective aldol [41] and Mannich reactions [42] as well as for the α-aminoxylation of carbonyl compounds under batch conditions [43]. Interestingly, the triazole linker between the polymer and the active unit, inherently resulting from the Cu(I)-catalyzed cycloaddition of

PEG-embedded KBr₃: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines

• Sanny Verma,
• Suman L. Jain and
• Bir Sain

Beilstein J. Org. Chem. 2011, 7, 1334–1341, doi:10.3762/bjoc.7.157

• –Alder reactions [22][23], intramolecular Michael reactions [24], intramolecular Mannich reactions onto iminium ions [25], tandem cyclopropane ring-opening/Conia-ene cyclizations [26], and aza-Prins-cyclization [27][28][29], have been reported for the synthesis of piperidines. However, these methods

Enantioselective synthesis of tricyclic amino acid derivatives based on a rigid 4-azatricyclo[5.2.1.0^2,6]decane skeleton

• Matthias Breuning,
• Tobias Häuser,
• Christian Mehler,
• Christian Däschlein,
• Carsten Strohmann,
• Andreas Oechsner and
• Holger Braunschweig

Beilstein J. Org. Chem. 2009, 5, No. 81, doi:10.3762/bjoc.5.81

• (five steps). The required endo-orientation of the acetic acid moiety in 8a•HCl was confirmed by the X-ray structure of the corresponding free base 8a•MeOH (Figure 4). A first evaluation of the bowl-shaped amino acid derivatives 7 and 8 in standard organocatalytic aldol and Mannich reactions showed that

• at a more remote position of the molecule, but still in close spatial proximity to the amino function. Examples are β-proline (4) [18][19], the bispidinium salt 5 [20], and the binaphthyl-derived amino acid 6 [21][22][23], which provided excellent enantioselectivities in several aldol and Mannich

• reactions. Our studies targeted the chiral, tricyclic amino acid derivatives 7 and 8 (Figure 2), which possess a central norbornane framework equipped with a 2-endo,3-endo-annelated pyrrolidine ring. Due to the constrained, bowl-shaped backbone, these compounds may possess high potential as β-turn-inducing