Stereodivergent Synthesis of 3-Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction

Water enables diastereodivergency in bispidine-based chiral amine-catalyzed asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones

Tuning diastereoselectivity is a great challenge in asymmetric catalysis for the inherent stereochemical bias of the substrates. Here, we report a diastereodivergent asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones catalyzed by a bispidine-based chiral amine catalyst, in which additional water switches the diastereoselectivity efficiently. Both chiral anti- and syn-benzosultams with potential anti-HIV-1 activity are obtained in excellent yields and good to excellent ee values. Control experiments and density functional theory (DFT) calculations were applied to study the diastereodivergent mechanism, which reveal that the diastereodivergent catalysis should be state-determined, and the water reverses the energies of states to realize the diastereodivergency. The findings are quite new and might inspire more diastereodivergent asymmetric synthesis.

A diastereodivergent asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones is realized by employing bispidine-based chiral amine as catalyst and additional water switching the diastereoselectivity.

Aymmetric Aza-Friedel-Crafts Reaction of Isatin-Derived Ketimines with Indoles Catalyzed by a Chiral Phase-Transfer Catalyst

A highly enantioselective aza-Friedel-Crafts reaction of 1H-indoles with isatin-derived N-Cbz-ketimines catalyzed by quinine-derived phase-transfer catalysts was developed. A series of chiral 3-aminobisindole compounds containing a tetrasubstituted stereocenter were constructed by this protocol in high yields (82-91%) and moderate to excellent enantioselectivities (46-94% ee).

One-step synthesis of rhodamine-based Fe3+ fluorescent probes via Mannich reaction and its application in living cell imaging

Four rhodamine-based fluorescent probes M1-M4 were synthesized in one step using Mannich reaction. The Mannich reaction based approach has the advantages of simplicity, good yield and excellent atomic economy. The structures were determined by ¹H NMR, ¹³C NMR, IR and HRMS. The probe M3 as a representative compound was characterized by single-crystal X-ray analyses. The fluorescence and absorbance spectra research of the probes demonstrated that they could be used as Fe³⁺-selective fluorescent probes with good sensitivity, excellent linearity, and outstanding anti-interference in acetonitrile/Tris-HCl buffer solution (3:7, V/V; pH = 7.4). Moreover, confocal laser scanning microscopy experiments have proven that the probe M3 was successfully used for fluorescence imaging in MCF-7 cells.

Recent advances in the catalytic synthesis of 3-aminooxindoles: an update

3-Substituted-3-aminooxindoles are versatile scaffolds and these motifs constitute the core structure of number of natural products and biologically active compounds.

Bifunctional squaramide catalyzed stereoselective Mannich reaction of α-azido ketones with isatin-derived ketimines

Bifunctional squaramide catalyzed asymmetric Mannich reaction of alpha-azido ketones and isatin derived ketiminines were established for the first time with high stereoselectivity. Adducts are valuable synthons for optically active heterocycles.

Catalytic enantioselective Michael addition of 2-substituted benzofuran-3-ones to 2-enoyl pyridines

An organocatalytic diastereo- and enantioselective synthesis of 2,2'-disubstituted benzofuran-3-ones bearing adjacent quaternary and tertiary stereocenters has been achieved through Michael addition of 2-substituted benzofuran-3-ones to 2-enoyl pyridines. Both the enantiomeric forms of the major diastereomer were obtained using l-proline derived squaramide and quinine derived bis squaramide with excellent yield (up to 98%) and stereoselectivities (up to 97 : 3 dr and 98% ee). The control experiment revealed that the presence and position of nitrogen atoms in the 2-enoylpyridine have played a crucial role in the stereochemical outcome of the product.