Synthesis of Substituted Indole from 2-Aminobenzaldehyde through [1,2]-Aryl Shift

Nickel-Catalyzed, Aminoquinoline-Directed Chemo- and Regioselective Carboamination of Unactivated Olefins with Organoboronic Acids and Anthranils

A nickel-catalyzed three-component carboamination of unactivated alkenes with organoboronic acids and anthranils has been achieved for the expedient synthesis of δ-aryl and γ-amino acid derivatives. The 8-aminoquinoline (AQ) directing group is crucial for the success of the reaction, and anthranil serves as an arylnitrene precursor in this conversion. This method features mild reaction conditions, good chemo- and regioselectivity, and a broad substrate scope with good functional group tolerance.

K2CO3-mediated annulation of 1,3-acetonedicarboxylates with 2-fluoro-1-nitroarenes: synthesis of indoles

The K2CO3-mediated one-pot reaction of 1,3-acetonedicarboxylates with 2 equiv. of substituted 2-fluoro-1-nitrobenzenes has been developed to synthesize various 2,3-dicarboxylate indoles via a tandem annulation pathway. In the effective reaction, one carbon-carbon double bond, one carbon-carbon single bond and one carbon-nitrogen single bond are formed under open-vessel conditions. DFT calculations are used to rationalize the plausible mechanisms.

Asymmetric formal C-C bond insertion into aldehydes via copper-catalyzed diyne cyclization

The formal C-C bond insertion into aldehydes is an attractive methodology for the assembly of homologated carbonyl compounds. However, the homologation of aldehydes has been limited to diazo approach and the enantioselective reaction was rarely developed. Herein, we report an asymmetric formal C-C bond insertion into aldehydes through diyne cyclization strategy. In the presence of Cu(I)/SaBOX catalyst, this method leads to the efficient construction of versatile axially chiral naphthylpyrroles in moderate to excellent yields with good to excellent enantioselectivities. This protocol represents a rare example of asymmetric formal C-C bond insertion into aldehydes using non-diazo approach. The combined experimental and computational mechanistic studies reveal the reaction mechanism, origin of regioselectivity and stereoselectivity. Notably, the chiral phosphine ligand derived from synthesized axially chiral skeleton was proven to be applicable to asymmetric catalysis.

NiH-Catalyzed Proximal-Selective Hydroamination of Unactivated Alkenes with Anthranils

The regioselective hydroamination of unactivated alkenes is a long-standing challenge in organic synthesis. Herein, we report a NiH-catalyzed proximal-selective hydroamination of unactivated alkenes with 8-aminoquinoline (AQ) as a bidentate auxiliary and anthranils as aminating reagents. A wide range of primary aryl amines bearing an ortho-carbonyl group were installed in both terminal and internal unactivated alkenes, delivering a variety of valuable β- and γ-amino acid building blocks, respectively, with excellent regiocontrol. The utility of this transformation was further demonstrated by the conversion of the multifunctionalized aryl amines into useful N-heterocycles.

Copper-catalyzed [4+1] cycloannulation of 2-aminochalcones with ethyl diazophenylacetates via ester rearrangement

Copper-catalyzed [4+1] cycloannulation of 2-aminochalcones with ethyl diazophenylacetates was developed, exhibiting a wide range of substrates and good tolerance of functional groups.

Design and synthesis of the first indole-based blockers of Panx-1 channel

Panx-1 is a membrane channel protein involved in some pathologies such as ischemic stroke, cancer and neuropathic pain, thus representing a promising therapeutic target. We present here a study aimed at obtaining the first class of selective Panx-1 blockers, a new topic for pharmaceutical chemistry, since all compounds used so far for the study of this channel have different primary targets. Among various scaffolds analyzed, the indole nucleous emerged, whose elaboration yielded interesting Panx-1 blockers, such as the potent 5-sulfamoyl derivatives 14c and 15b (I% = 100 at 50 μM). In vivo tests performed in the mouse model of oxaliplatin-induced neuropathy, demonstrated that the hypersensitivity was completely reverted by treatment with 15b (1 nmol, administered intrathecally), suggesting a relationship between this effect and the channel blocking ability. Finally, we decided to perform a virtual screening study on compounds 5b, 6l and 14c using a recently resolved cryo-EM structure of hPanx-1 channel, to try to relate the potency of our new inhibitors.

Electrophilic Amination with Anthranils through Thioamide-Assisted Cobalt(III)-Catalyzed C(sp3)–H Activation

Cobalt(III)-catalyzed electrophilic amination of inert C(sp3)–H bonds of weakly coordinating thioamides with readily accessible anthranil derivatives was accomplished under mild conditions, with good functional group tolerance, thus providing various amino aldehydes and amino ketones. Moreover, our protocol with the versatile [Cp*Co(MeCN)3][SbF6]2 features excellent atom-economy and oxidant-free conditions, and allows facile late-stage functionalization.

Asymmetric Synthesis of Chiral 1,2-Amino Alcohols and Morpholin-2-ones from Arylglyoxals

Chiral 1,2-amino alcohols are privileged scaffolds with important applications as drug candidates and chiral ligands. Although various methods for the preparation of this structural motif have been reported, these methods are limited because of the use of precious metals and ligands. Here, we report a practical and high yielding synthesis of chiral 1,2-amino alcohols using arylglyoxals and pseudoephedrine auxiliary. This reaction is catalyzed by a Brønsted acid and provides morpholinone products in high yields and selectivities. The morpholine ring was converted into 1,2-amino alcohols in a two-step protocol.

Site-selective Cp*Rh(iii)-catalyzed C–H amination of indolines with anthranils

The pyrimidinyl-directed C–H functionalization of indolines with anthranils as amination sources under rhodium(iii) catalysis is described to afford a range of C7-aminated indoline derivatives with excellent site-selectivity and functional group compatibility.

Rh(iii)-Catalyzed direct C-7 amination of indolines with anthranils

An effective and fascinating method has been developed for direct C-7 amination of indolines under Rh(iii) catalysis with anthranils.

Synthesis of 6,12-Epiminodibenzo[b,f][1,5]diazocines via an Ytterbium Triflate-Catalyzed, AB2 Three-Component Reaction

An efficient and selective procedure for the synthesis of epiminodibenzo[b,f][1,5]diazocines involving a AB₂ three-component reaction is developed. Two equivalents of suitably substituted 2-aminoarylaldehydes reacted with arylamines in the presence of Yb(OTf)₃ to afford the desired products in high yields. The reaction is highly atom-economic and waste-free, in addition to allowing the generation of two heterocyclic rings and four C-N bonds in a single operation. Significantly, this approach is complementary to the existing literature procedures, affording arylamine-derived products that could not be accessed previously. A plausible mechanism is proposed involving an imine formation-intermolecular annulation-intramolecular iminium ion cyclization sequence.

Collective Synthesis of 3-Acylindoles, Indole-3-carboxylic Esters, Indole-3-sulfinic Acids, and 3-(Methylsulfonyl)indoles from Free (N-H) Indoles via Common N-Indolyl Triethylborate

A general and direct C3 functionalization of free (N-H) indoles with readily available electrophiles such as acid chlorides, chloroformates, thionyl chloride, and methylsulfonyl chloride via a common N-indolyl triethylborate intermediate is reported. The reaction proceeds smoothly under mild conditions in up to 93% yield. Indoles with substituents at the C2, C4, C5, C6, and C7 positions are well tolerated. The easy accessibility of a variety of important 3-acylindoles, indole-3-carboxylic esters, indole-3-sulfinic acids, and 3-(methylsulfonyl)indoles demonstrates the high degree of compatibility and practicability of this method.