Cu-Fe Spinels: First Heterogeneous and Magnetically Recoverable Catalyst for the Ferrier Rearrangement of 2-Nitroglycals

Abstract

Cu-Fe spinels promoted the Ferrier rearrangement of 2-nitroglycals with several O-nucleophiles. 2,3-Unsaturated carbohydrate derivatives were prepared by the reaction of 3,4,6-tri-Oacetyl- 2-nitroglucal and alcohols in the presence of 5 % of CuFe2O4. After separation of the catalyst with an external magnet, the reaction products were obtained in good yields and high stereo and regioselectivity. Also, S- and heterocyclic C-3 substituted 2-nitro-endo-glycals could be prepared by this method.

A General Strategy for the Stereoselective Synthesis of Pyrrole‐Fused Chiral Skeletons: [3+2] Cycloaddition with 2‐Nitro‐2,3‐Unsaturated Glycosides

“…((2R,3S,6S)‐3‐acetoxy‐6‐isopropoxy‐5‐nitro‐3,6‐dihydro‐2H‐pyran‐2‐yl)methyl acetate (3 r) : [14a] Colorless syrup. 1 H NMR (500 MHz, CDCl 3 ) δ 7.15 (d, J =2.2 Hz, 1H), 5.66 (s, 1H), 5.55 (dd, J =9.3, 1.8 Hz, 1H), 4.31–4.27 (m, 1H), 4.27–4.23 (m, 2H), 4.07 (m, J =6.2 Hz, 1H), 2.14 (s, 3H), 2.10 (s, 3H), 1.25 (dd, J =14.6, 6.2 Hz, 6H).…”

Synthesis of 2-Nitro-2,3-Unsaturated Glycosides by a Nanomagnetic Catalyst Fe3O4@C@Fe(III)

“…The structure and stereochemistry of the rearrangement products were elucidated by NMR and mass spectroscopy and were subsequently compared with the reported data ( Dharuman et al, 2013 ; Lafuente et al, 2019 ; Jiang et al, 2021 ). It was noteworthy that the stereoselectivity of 2-nitro-2,3-unsaturated glycoside compounds was confirmed as α: β > 19:1 by 1 H NMR.…”

“…Based on the experimental results and literature studies, a reaction mechanism may be proposed as follows ( Figure 3 ). ( Dharuman et al, 2013 ; Lafuente et al, 2019 ; Jiang et al, 2020b ; Jiang et al, 2021 ): As we know, a halogen substituent at the C-2 position of the glycals has a remarkable effect, and those electron-withdrawing groups would reduce the electron density of the oxocarbenium intermediate, which is commonly assumed as the intermediate cation in the Ferrier rearrangement ( Dong et al, 2019 ). Thus, under the nanocatalysis of Fe 3 O 4 @C@Fe(III), C3 site deacylation in 2-nitro-glucal would occur very slowly and electron transfer would occur in a different way, with the aid of the nucleophiles.…”

“…However, the number of substrates suitable for this reaction condition was only five, and the yield was generally not very high (57–74%), probably due to the occurrence of deacylation side reaction under alkaline condition. In 2018, Lafuente et al (2019 ) promoted the Ferrier rearrangement of 2-nitro glycals with several O -nucleophiles in the presence of CuFe 2 O 4 . The catalyst could be separated by an external magnet, while the reaction products were obtained in good yields and high stereoselectivity.…”

Controllable 1,3-Bis-Functionalization of 2-Nitroglycals with High Regioselectivity and Stereoselectivity Enabled by a H-Bond Catalyst

“…Compared with benzylated 2-nitroglycals, acetylated analogues are easier to prepare from corresponding oligosaccharides in two steps, , and the acetyl group, after the reaction, can be readily removed under mild conditions. However, due to its potentially high reactivity, especially the side reaction of Ferrier rearrangement under conventional glycosylation conditions, ,− the application of acetylated 2-nitroglycals in carbohydrate chemistry is much less developed. In 2013, by using DMAP as a catalyst, Vankar’s group found that acetylated 2-nitroglycals can undergo selective functionalization at the C1- or C3-position based on the properties of nucleophiles.…”