A highly efficient method to access unprotected C-3 bifunctional quaternary 3-allyl-3-(amino)oxindoles

A highly efficient Rh(II) catalyzed non-radical protocol to access NH-free C-3 bifunctional oxindoles, which possess 3-allyl and 3-amino simultaneously, was first achieved by employing an intermolecular [2,3]-sigmatropic rearrangement reaction between diazooxindoles and tertiary allylic amines. Utilizing readily available allylamines as the nitrogen and allyl source concurrently, a wide range of bio-active 3-allyl-3-(amino)oxindoles were obtained in excellent yields under very mild reaction conditions; meanwhile, the TON can be up to 90 000. Our study addresses a gap in the literature by investigating intermolecular rearrangements of ammonium ylides with diazoamides, which have been relatively understudied.

Enantioselective Benzylation and Allylation of a Crucial Synthon of 3-Amino Oxindole Schiff Base Promoted by a Cinchonidinium Phase Transfer Catalyst to Enable the Effective Preparation of Chiral Quaternary 3-Amino Oxindoles

3-Amino oxindole Schiff base has been used as an efficient and crucial synthon for highly enantioselective benzylation and allylation with benzyl bromides and allyl bromides in the presence of a 1,3-bis[O(9)-allylcinchonidinium-N-methyl]-2-fluorobenzene dibromide phase transfer catalyst under mild reaction conditions. A broad series of chiral quaternary 3-amino oxindoles were smoothly obtained in good to excellent yields with excellent enantioselectivities (up to 98% ee) with broad substrate generality. A typical scale-up preparation and subsequent Ullman coupling reaction were also smoothly performed, and a special and important chiral spirooxindole benzofuzed pyrrol scaffold with potential pharmaceutical and organocatalytic activities was successfully obtained.

Protonated Chiral 1,2-Diamine Organocatalysts for N-Selective Nitroso Aldol Reaction

The introduction of nitrogen to carbonyl groups is considered both challenging and highly desirable by those who work in the field of organic synthesis. In this study, a diphenylethylenediamine-derived catalyst demonstrating N-selectivity was designed using a quantum calculation for the nitroso aldol reaction. The reductive monoalkylation of (R,R)-(+)-1,2-diphenylethylenediamine afforded an organic chiral diamine catalyst in high yield. The expected reaction mechanism for the nitroso aldol reaction was determined, and the product and solvent conditions were optimized through quantum calculations. The calculation results revealed that the enantioselectivity is determined by the hydrogen bond between the alkyl substituent of the chiral diamine and the oxygen of the aromatic aldehyde on the ammonium moiety. The reaction was found to proceed optimally in the presence of 5 mol % catalyst at −10 °C in brine. Using these conditions, an eco-friendly nitroso aldol reaction was performed in which the organic catalyst and cyclohexanone formed enamine. Nitrosobenzene, activated by hydrogen bonding with an ammonium catalyst, was used to minimize the steric hindrance between the catalyst and the reactant, resulting in high enantioselectivity. A nitroso aldol product with high N-selectivity and enantioselectivity (98% ee) was obtained in 95% yield. The catalyst developed in this study provides a less expensive and more environmentally friendly alternative for the nitroso aldol reaction.

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

A practical enantioselective N-selective nitroso aldol reaction of α-methylmalonamates with a nitrosoarene is reported. The reaction employs the Takemoto thiourea catalyst for the induction of enantioselectivity, and the corresponding optically active oxyaminated malonamates were obtained in reasonably good yields.

Highly efficient synthesis of chiral quaternary 3-aminooxindoles promoted by zinc(ii) chloride via Et2Zn-catalysed addition of Grignard reagents to isaltin-derived N-tert-butanesulfinyl ketimines

An approach to chiral quaternary 3-aminooxindoles via Et₂Zn catalyzed diastereoselective addition of various Grignard reagents to broad isaltin-derived N-tert-butanesulfinyl ketimines promoted by zinc(ii) chloride.

Bis(imidazolidine)pyridine-NiCl2 Catalyst for nitro-Mannich reaction of isatin-derived N-Boc ketimines: asymmetric synthesis of chiral 3-substituted 3-amino-2-oxindoles

An (S,S)-diphenyldiamine-derived bis(imidazolidine)pyridine (PyBidine)-NiCl2 complex catalyzed the nitro-Mannich reaction of isatin-derived N-Boc ketimines to construct a chiral quaternary aminocarbon center at the C3 position of oxindoles in yields of up to 99% with 95% ee.

Asymmetric construction of quaternary stereocenters by magnesium catalysed direct amination of β-ketoesters using in situ generated nitrosocarbonyl compounds as nitrogen sources

An oxophilic magnesium salt in combination with a chiral N,N′-dioxide ligand switches the chemoselectivity of an ambident nitrosocarbonyl species to nitrogen for the highly enantioselective α-amination of β-ketoesters.

Asymmetric Michael/cyclization tandem reaction of 4-hydroxycoumarin with β-nitroalkenes catalyzed by chiral bifunctional thioureas

The first asymmetric Michael/cyclization tandem reaction of 4-hydroxycoumarin with nitroolefins catalyzed by chiral bifunctional thioureas was reported and 2,3-dihydrofuro[3,2-c]-coumarin adducts have been obtained in moderate yields (53-75%) and good enantioselectivities (64-90% ee).