Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• catalysts such as β-isocupreidine (β-ICD) have found limited use in combination with photoredox catalysis, likely due to their tendency to oxidise to form iminium ions. However, Jiang et al. have developed a process using acrolein (94) in the presence of tetrahydro-β-carbolines (THCs) 95 or THIQs 96 and a

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• N-Boc-isatin imines 3 with acrolein (35) promoted by 15 mol % of β-isocupreidine at −40 °C in a 1:1 mixture of toluene and CPME as solvent [57]. As shown in Scheme 11, the corresponding chiral 3-amino-2-oxindoles 36 were synthesized with uniformly excellent enantioselectivities (95–98% ee) and

• -isocupreine as organocatalyst instead of 15 mol % of β-isocupreidine (Scheme 11) in this reaction resulted in the formation of the corresponding (R)-configured products ent-36 with good to high enantioselectivities (83–95% ee) and moderate to good yields (37–79%), as shown in Scheme 12. The stereoselectivity

• maleimides 37 using β-isocupreidine as catalyst [61]. It must be noted that maleimides as Morita–Baylis–Hillman donors were challenging in these reactions since they are more usually employed as Michael acceptors. As shown in Scheme 13, a wide variety of chiral 3-amino-2-oxindoles 38 was synthesized in

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• . found that β-isocupreidine (β-ICD, cat. 22) can efficiently catalyze the Morita–Baylis–Hillman (MBH) reaction of isatins with maleimides to generate the 3-substituted 3-hydroxyoxindoles in excellent yields (up to 96% yield) and with excellent enantioselectivity (up to >99% ee) under mild conditions

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• using β-isocupreidine (β-ICPD). In the first of these, α-substituted nitoacetates 73 are used [56], and in the second 3-thiooxindoles 75 are employed (Scheme 18) [57]. Unfortunately, in neither of these papers is the absolute stereochemistry elucidated. Finally, Meng and co-workers used cupreidine (CPD

• with cupreine, cupreidine, β-isoquinidine and β-isocupreidine derivatives. The original 6’-OH cinchona alkaloid organocatalytic MBH process, showing how the free 6’-OH is essential for coordination to the substrate. Use of β-ICPD in an aza-MBH reaction. (a) The isatin motif is a common feature for MBH

• -amination using β-ICPD. Meng’s cupreidine catalyzed α-hydroxylation. Shi’s biomimetic transamination process for the synthesis of α-amino acids. β-Isocupreidine catalyzed [4 + 2] cycloadditions. β-Isocupreidine catalyzed [2+2] cycloaddition. A domino reaction catalyst by cupreidine catalyst CPD-30. (a

Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

• Qing He,
• Gu Zhan,
• Wei Du and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2016, 12, 309–313, doi:10.3762/bjoc.12.33

• in diverse biologically active substances. Here 7-azaisatins turned out to be more efficient electrophiles than the analogous isatins in the enantioselective Morita–Baylis–Hillman (MBH) reactions with maleimides using a bifunctional tertiary amine, β-isocupreidine (β-ICD), as the catalyst. This route

• allows a convenient approach to access multifunctional 3-hydroxy-7-aza-2-oxindoles with high enantiopurity (up to 94% ee). Other types of activated alkenes, such as acrylates and acrolein, could also be efficiently utilized. Keywords: 7-azaisatins; β-isocupreidine; bifunctional catalysis; maleimide; MBH

• acrolein catalyzed by β-isocupreidine (β-ICD) was reported by the Zhou group [5], isatin derivatives, as highly activated electrophiles, have been utilized by other groups for similar transformations with acrylates or acrylamides, affording the 3-hydroxyoxindole derivatives with moderate to excellent

Asymmetric organocatalytic decarboxylative Mannich reaction using β-keto acids: A new protocol for the synthesis of chiral β-amino ketones

• Chunhui Jiang,
• Fangrui Zhong and
• Yixin Lu

Beilstein J. Org. Chem. 2012, 8, 1279–1283, doi:10.3762/bjoc.8.144

• , entry 1). Quinine-derived sulfonamide [40], β-isocupreidine (β-ICD) [41][42] and biscinchona alkaloid (DHQ)2AQN were all found to be poor catalysts (Table 1, entries 2–4). On the other hand, cinchona alkaloid derived bifunctional thiourea tertiary amine catalysts afforded much improved results (Table 1

Organocatalytic asymmetric allylic amination of Morita–Baylis–Hillman carbonates of isatins

• Hang Zhang,
• Shan-Jun Zhang,
• Qing-Qing Zhou,
• Lin Dong and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2012, 8, 1241–1245, doi:10.3762/bjoc.8.139

• isatins to obtain 2-oxindoles bearing a C3-quaternary chiral center, by the catalysis of chiral tertiary amines, β-isocupreidine (β-ICD) or its derivatives [23][24]. We envisaged that such a catalytic strategy should be applicable to the allylic amination of the corresponding MBH carbonates [25][26][27

• with N-benzyloxycarbonyl and O-benzyl groups [29] was applied in diethyl ether (Table 1, entry 1). Subsequently, an array of tertiary amines derived from quinidine was explored to introduce chirality into the product. While poor enantioselectivity was obtained when β-isocupreidine 1a (β-ICD) or β