Organocatalytic Enantioselective Amination of 2-Substituted Indolin-3-ones: A Strategy for the Synthesis of Chiral α-Hydrazino Esters

Enantioconvergent and diastereoselective synthesis of atropisomeric hydrazides bearing a cyclic quaternary stereocenter through ternary catalysis

An efficient and highly enantioconvergent and diastereoselective ternary catalysis in a one-pot process is reported, which represents an integrated strategy for the synthesis of atropisomeric hydrazides with defined vicinal central and axial chirality from readily available racemic α-amino-ynones, azodicarboxylates, and Morita-Baylis-Hillman (MBH) carbonates. This method utilizes in situ-generated racemic pyrrolin-4-ones via hydroamination of racemic α-amino-ynones by AuCl catalysis as a novel and versatile C1 synthon, which engage commercially available azodicarboxylates to generate amination products in high yields and uniformly excellent enantioselectivities under the catalysis of a chiral phosphoric acid. Following amination, N-alkylation catalyzed by diastereoselective organocatalyst afforded axially chiral hydrazides with excellent diastereoselectivities (>98 : 2 dr). The synthetic utility of the amination products and axially chiral hydrazides was also demonstrated by their facile conversion to diverse molecules in high yields with excellent stereopurity. Density functional theory calculations were performed to understand the origin of diastereoselectivity.

Pd-Catalyzed Asymmetric Allylation Reaction of 2-Aryl-3H-indol-3-ones with Allyltrimethylsilane

An efficient method for the first ene-reaction of 2-aryl-3H-indol-3-ones with allyltrimethylsilane has been developed for the first time. The reaction proceeded under the catalysis of Pd(OAc)2 and chiral phosphoric ligand L11 in the presence of Cu(CF3COO)2·XH2O, PivOH, and 5 Å molecular sieves in DMSO at 60 °C. The present methodology can avoid the impact of amine products generated by the reaction on the catalyst, and at the same time, the high catalytic activity of classical palladium catalysts still has catalytic ability for low electrophilic keto-imines. The desired products were furnished in excellent yields with good enantioselectivity.

KI-Catalyzed C(sp3)-H Amination and Acyloxylation of Indolin-3-ones Using Air as the Oxidant

We have developed an efficient and green strategy for the synthesis of C2-amino indolin-3-ones and C2-acyloxy indolin-3-ones via KI-catalyzed C(sp3)-H amination and acyloxylation of indolin-3-ones using air as the oxidant. The reaction provides straightforward access to 2-substituted indolin-3-ones by the direct functionalization of indolin-3-ones at the C2 position under mild conditions. Moreover, the conditions enable direct functionalization of a range of complex pharmaceuticals, providing attractive products for medicinal chemistry programs.

Chiral π-Cu(II) Catalysts for the Enantioselective α-Amination of N-Acyl-3,5-dimethylpyrazoles

We report the highly enantioselective α-amination of N-acyl-3,5-dimethylpyrazoles with dialkyl azodicarboxylates, catalyzed by in situ generated π-Cu(II) complexes that consist of Cu(OTf)₂ and N-(5H-dibenzo[a,d][7]annulen-5-yl)-l-alanine-derived amides, to give the corresponding products as d-α-amino acid derivatives (up to >99% yield and 99% ee). The site-selectivity and enantioselectivity can be satisfactorily explained by the coordination of dialkyl azodicarboxylate with π-Cu(II) complex. The synthetic potential of this one-pot transformation to the α-amino ester is also described.

Anodic C(sp3)-H Acyloxylation of Indolin-3-ones Enabled by Oxidant-Free Cross-Dehydrogenative C(sp3)-O Coupling

An efficient anodic C(sp³)-H acyloxylation protocol has been established via intermolecular cross-dehydrogenative C(sp³)-O coupling. The protocol provides various C2-acyloxy indolin-3-ones without the addition of metal catalysts and external oxidants because indolin-3-ones can be directly oxidized at the anode. The effective application of several medical drugs and the realization of the gram-scale experiment have proven the practicality of this protocol.

A solid-supported organocatalyst for asymmetric Mannich reaction to construct C2-quaternary indolin-3-ones

A simple and novel solid-supported organocatalyst from a 2-chlorotrityl chloride resin-immobilized 4-hydroxyproline was developed, and this organocatalyst has been used for the asymmetric Mannich reaction of 2-aryl-3H-indol-3-ones and aldehydes/ketones. A series of C2-quaternary indolin-3-ones were prepared in good yields (up to 83%) and with excellent diastereoselectivities (up to 20 : 1) and enantioselectivities (up to 99% ee). In addition, the organocatalyst can be recovered by simple filtration and also be reused for the asymmetric Mannich reaction without significant loss of catalytic efficiency.

A simple and novel solid-supported organocatalyst from a 2-chlorotrityl chloride resin-immobilized 4-hydroxyproline was developed, which has been used for the asymmetric Mannich reaction of 2-aryl-3H-indol-3-ones and aldehydes/ketones.

Enantioselective fluorination of 3-indolinone-2-carboxylates with NFSI catalyzed by chiral bisoxazolines

A chiral Cu(i)-bisoxazoline complex catalyzed enantioselective electrophilic fluorination of 3-indolinone-2-carboxylates with NFSI has been accomplished to produce chiral 2-fluoro-3-indolinone-2-carboxylates in good yields with excellent enantioselectivities. This is the first report on the enantioselective fluorination of 2-substituted 3-indolinones using a chiral Cu(i)-bisoxazoline complex.

Unexpected Insertion of Nitrogen into a C-C Bond: Access to 2,3-Disubstituted Quinazolinone Scaffolds

A novel, practical, highly efficient, and transition metal free nitrogen insertion reaction for the synthesis of 2,3-disubstituted quinazolinone derivatives was developed. Diverse functionalized 3-indolinone-2-carboxylates and nitrosoarenes with a wide range of substituted nitrosobenzenes, nitrosopyridines, dibenzofuranyl, or dibenzothienyl nitroso compounds worked smoothly to give 2,3-disubstituted quinazolinone derivatives in good to excellent yields (69-98%). A gram-scale reaction was achieved, and an afloqualone analogue was synthesized under the mild reaction conditions.

Enantioselective amination of 4-alkylisoquinoline-1,3(2H,4H)-dione derivatives

A mild and efficient enantioselective amination of 4-alkylisoquinoline-1,3(2H,4H)-dione derivatives was established, which is compatible with a broad range of substrates and delivers the final products in excellent yields (up to 99%) and ee values (up to 99%) with low catalyst loading (down to 1 mol%). The synthetic potential of this methodology was also demonstrated in the gram scale level.

Enantioselective α-Amination of Acyclic 1,3-Dicarbonyls Catalyzed by N-Heterocyclic Carbene

Herein, we describe a method for the catalytic enantioselective α-amination of α-substituted acyclic 1,3-ketoamides and 1,3-amidoesters that affords the products possessing N-substituted quaternary stereocenters with a chiral N-heterocyclic carbene (NHC). The reaction is based on the utilization of an intrinsic Brønsted base characteristic of NHC that enables the catalytic formation of a chiral ion pair comprising the enolate and the azolium ion. A series of challenging open-chain α-substituted 1,3-dicarbonyls are aminated via this method with ee's of ≤99%.

Direct enantioselective Mannich reactions of α-azido cyclic ketones: asymmetric construction of chiral azides possessing an α-quaternary stereocenter

Direct enantioselective Mannich reactions of α-azido cyclic ketones with aldimines are realized through chiral phosphoric acid catalysis, which generate chiral azides possessing an α-quanternary stereocenter with complete regioselectivities and high diastereoselectivities and enantioselectivities.

Chiral Phosphoric Acid-Catalyzed Synthesis of Fluorinated 5,6-Dihydroindolo[1,2- c]quinazolines with Quaternary Stereocenters

A chiral phosphoric acid-catalyzed enantioselective synthesis of fluorinated 5,6-dihydroindolo[1,2- c]quinazolines has been developed by a condensation/amine addition cascade from 2-(1 H-indolyl)anilines and fluorinated ketones, giving the fluorinated aminals with quaternary stereogenic centers with excellent yields and up to 97% ee. A series of the fluorinated aromatic, aliphatic ketones, and ethyl trifluoropyruvate are suitable.

Organocatalytic Enantioselective Mannich Reaction: Direct Access to Chiral β-Amino Esters

An asymmetric Mannich reaction has been developed to generate chiral β-amino esters in good yields with excellent enantiomeric excesses (ee, up to 99%) using a chiral bifunctional thiourea catalyst derived from (R,R)-cyclohexyldiamine. This is the first report on the addition of 3-indolinone-2-carboxylates to N-Boc-benzaldimines generated in situ from α-amidosulfones, which proceeds under mild conditions.

Oxidative Asymmetric Aza-Friedel-Crafts Alkylation of Indoles with 3-Indolinone-2-carboxylates Catalyzed by a BINOL Phosphoric Acid and Promoted by DDQ

An asymmetric aza-Friedel-Crafts alkylation reaction between indoles and indolenines that were derived in situ from 3-indolinone-2-carboxylates has been developed by using 3,3'-bis(triphenylsilyl)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate as a catalyst. The reaction proceeded under mild conditions and provided chiral indol-3-yl-3-indolinone-2-carboxylate derivatives in good yields with excellent ee values (up to 98.6 %). Similarly, the Mannich-type addition of indoline-3-ones to indolenines provided heterodimers with vicinal chiral quaternary centers. This method was successfully applied to the construction of the core structure of trigonoliimine C.

Enantioselective amination of nitroolefins under base-free and water-rich conditions using chiral bifunctional phase-transfer catalysts

A highly enantioselective amination of nitroolefins was realized with l-tert-leucine derived squaramide-scaffold bifunctional phase-transfer catalysts under base-free and water-rich conditions.

Palladium-catalyzed direct C(sp3)–H arylation of indole-3-ones with aryl halides: a novel and efficient method for the synthesis of nucleophilic 2-monoarylated indole-3-ones

A novel and efficient method for the synthesis of nucleophilic 2-monoarylated indole-3-ones via palladium-catalyzed direct C(sp³)–H arylation of indole-3-ones with aryl halides has been developed.

Asymmetric amination of 2-substituted indolin-3-ones catalyzed by natural cinchona alkaloids

The natural quinine-catalyzed enantioselective amination of 2-substituted indolin-3-ones with azodicarboxylates has been developed.