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Unique examples of aza-Heck-based C(sp3)-H functionalization cascades are described. Under Pd(0)-catalyzed conditions, the aza-Heck-type cyclization of N-(pentafluorobenzoyloxy)carbamates generates alkyl-Pd(II) intermediates that effect C(sp3)-H palladation en route to cyclopropanes. Key factors that control the site selectivity of the cyclopropanation process have been elucidated such that selective access to a wide range of ring- or spiro-fused systems can be achieved.

Unique examples of aza-Heck-based C(sp

A 12-step asymmetric synthesis of thromboxane B2 (TxB2) from 2,5-dimethoxytetrahydrofuran is described. The synthesis employs our organocatalytic aldol reaction of succinaldehyde to give a key bicyclic enal intermediate. From here, the synthetic strategy involves a conjugate addition of an alkenyl side chain to the bicyclic enal, Baeyer–Villiger oxidation, and a highly Z-selective Wittig olefination of a hemiacetal. Key to success was minimizing redox operations and the manipulation of functional groups in the correct order.

Dearomatization reactions allow the direct synthesis of structurally complex sp3 -rich molecules from readily available "flat" precursors. Established dearomatization processes commonly involve the formation of new C-C bonds, whereas methods that enable the introduction of C-N bonds have received less attention. Because of the privileged position of nitrogen in drug discovery, significant recent methodological efforts have been directed towards addressing this deficiency. Consequently, a variety of new processes are now available that allow the direct preparation of sp3 -rich amino-containing building blocks and scaffolds. This review gives an overview of C-N bond forming dearomatization reactions, particularly with respect to scaffold assembly processes. The discussion gives historical context, but the main focus is on selected methods that have been reported recently.

Bicyclo[1.1.1]pentanes (BCPs) have found application as bioisosteres of aromatic rings in drug development. However, catalytic construction of this motif with adjacent stereocenters with high enantioselectivity from readily available starting materials still constitutes a significant synthetic challenge. Herein we report a direct stereoselective synthesis of α-chiral allylic BCPs by 1,3-difunctionalization of [1.1.1]propellane with Grignard reagents and allyl carbonates using iridium catalysis. This mild protocol proceeds via initial organometallic addition to [1.1.1]propellane followed by asymmetric allylic substitution, providing the products with high enantioselectivities over a broad range of substrates. Further derivatization of the products demonstrates the applicability of this method to the preparation of structurally diverse libraries of chiral BCP derivatives.

Norstatine derivatives are of important value in pharmaceutical science. However, their catalytic asymmetric synthesis is rare. We developed a sustainable method via chiral phosphoric acid (CPA)-[Rh(OAc)2]2 co-catalyzed multi-component reactions (MCR) of diazoacetates with alcohol/water and imines. This method allows us to synthesize a library of 45 norstatines with excellent enanotioselectivites and broad substrate scope which includes anti-α-aryl-norstatines 11-1, anti-α-alkyl-norstatines 11-2, syn-α-hydro-norstatines 11-3 and syn-α-aryl-norstatines 11-4. The sustainability of this method lies in the reliable scalability, improved safety, and reusable [Rh(OAc)2]2 catalyst. The synthetic value of norstatine derivatives was demonstrated by preparing oxazolinone 14, ezetimibe analogue 15, and Taxol C-13 chain 16. Mechanistic study reveals that the synergetic catalysis of CPA and [Rh(OAc)2]2 is essential to maintain chemo- and enantioselectivity. Control experiments support the mechanism where the reactions proceed through the trapping of hyper-reactive oxonium ylides with imines. Shortly, we report herein the sustainable catalytic enantioselective synthesis of both syn- and anti-norstatine derivatives. We believe that this method might shed light on the sustainable synthesis of norstatine derivative-based drug candidates.

1,3-Disubstituted bicyclo[1.1.1]pentanes (BCPs) are valuable bioisosteres of para-substituted aromatic rings. The most direct route to these structures is via multicomponent ring-opening reactions of [1.1.1]propellane. However, challenges associated with these transformations mean that difunctionalized BCPs are more commonly prepared by multistep reaction sequences with BCP-halide intermediates. Herein, we report three- and four-component 1,3-difunctionalizations of [1.1.1]propellane with organometallic reagents, organoboronic esters, and a variety of electrophiles. This process is achieved by trapping intermediate BCP-metal species with boronic esters to form boronate complexes, which are versatile intermediates whose electrophile-induced 1,2-metallate rearrangement chemistry enables a broad range of C-C bond-forming reactions.

Catalyst effectiveness for metal carbene formation and reactions has been surveyed using N-(tert-butyl)-3-[(tert-butyldimethylsilyl)oxy]-2-diazo-N-(4-chlorobenzyl)but-3-enamide in the formation of the products from both intramolecular C–H insertion and aromatic cycloaddition. Both products are indicators of metal carbene intermediates, and this system provides a means to assess catalysts for metal carbene formation. Donor–acceptor cyclopropene production from the reactant enoldiazoacetamide has been monitored to assess its formation, and the independently formed cyclopropene has also been used to assess metal carbene formation. Catalysts of rhodium(II), copper(I), silver(I), Pd(II), cationic Au(I), and Zn(II) convert the enoldiazoacetamide to the donor–acceptor cyclopropene which serves as the resting state for the intermediate metal carbene, and both the enoldiazoacetamide and its derivative cyclopropene give the same ratios of insertion to cycloaddition products. Catalysts of copper(II) and ruthenium(II...

Chiral cyclopentane-fused indolines are synthesized with high regio- and enantiocontrol by formal [3 + 2]-annulation reactions of indoles and electrophilic enol carbenes. High enantioselectivity and exclusive regiocontrol occurred with enoldiazoacetamides using a less sterically encumbered prolinate-ligated dirhodium(II) catalyst in reactions with N-substituted indoles without substituents at the 2- or 3-positions via a selective vinylogous addition process. In this transformation, donor-acceptor cyclopropenes generated from enoldiazoacetamides serve as the carbene precursors to form metal carbene intermediates.

A rhodamine B-based sensor (RS) was designed and synthesized by a combination of the spirolacton rhodamine B (fluorophore) and multidentate chelates (ionophore) with high affinity towards Hg2+. In the presence of Hg2+, the resulting red-orange fluorescence (under UV light) and naked eye red color of RS are supposed to be used for quantitative and qualitative measurement of Hg2+. Further fluorescent titration and analysis demonstrate that RS can selectively detect Hg2+ within 1 s with a low limit of detection (LOD) of 16 nM in acetonitrile media, meanwhile, the association constant (Ka) was calculated to be 0.32 × 105 M−1. More importantly, the resultant complex (RSHg) of RS and Hg2+ has also been successfully applied to detect limited water content in acetonitrile solution.

An efficient rhodium(II)-catalyzed three-component reaction of 3-diazooxindoles, indoles and formalin was reported. With this transformation, a series of 3-(hydroxymethyl)-3-indol-3′-yloxindoles were easily afforded in good to excellent yields. The resulted 3-(hydroxymethyl)-3-indol-3′-yloxindole could be easily converted to the key intermediate for the total synthesis of gliocladin C.

A highly diastereo- and enantioselective four-component reaction of a diazo ketone with two molecules of anilines and ethyl glyoxylate was achieved under Rh2(OAc)4 and chiral phosphoric acid cocatalyzed conditions. This transformation proceeds through a Mannich-type trapping of the ammonium ylide generated from metal carbene and one molecule of aniline with iminoester derived from another molecule of aniline and ethyl glyoxylate. With this method, a series of chiral α,β-diamino acid derivatives were efficiently constructed in good yields and with good to excellent diastereo- and enantioselectivities.

Highly chemoselective and enantioselective one-pot reactions involved in the oxidative functionalization of Csp3–H bonds adjacent to nitrogen atoms in N-aryl glycine esters were developed. The method provided rapid access to a variety of highly functionalized β-hydroxyl-α-amino acid derivatives from simple starting materials under mild conditions.

This new multicomponent reaction allows the selective synthesis of pyrrolidines or the corresponding linear α-amino ester derivatives by controlling the addition sequence of the substrates.

Highly chemoselective and enantioselective one-pot reactions involved in the oxidative functionalization of C

Protein tyrosine phosphatase 1B (PTP1B) has been proposed to be an effective target for the treatment of both type II diabetes and obesity. However, no PTP1B inhibitor has come into clinic application. Herein, we report mixed 3,3'-bisindoles as novel PTP1B inhibitors with low micromole-ranged inhibitory activity. The best active compound 9f inhibited PTP1B activity with an IC

The corresponding title compounds are obtained through a metal—carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates.

A new strategy for the synthesis of N-alkoxycarbonyl aryl α-imino esters in the presence of dirhodium tetraacetate [Rh2(OAc)4] is reported to produce the desired compounds in high yield (up to 96%) under mild reaction conditions. The application of the synthetic method is demonstrated in enantioselective reduction and Friedel–Crafts reaction of indoles to afford the corresponding chiral arylglycines and indole derivatives, respectively, in high yield and excellent ee.

Imines, diazo compounds, and water undergo a rhodium/chiral Broensted acid catalyzed reaction to give the title compounds with good threo-selectivity and up to 97% enantioselectivity.

A Rh(II)/chiral phosphoric acid co-catalyzed four-component reaction of indoles, 3-diazooxindoles, aryl amines, and glyoxylate affords the title compounds efficiently with excellent diastereoselectivity (

The title reaction is described to yield bicyclo[3.2.2]nonatriene derivatives (II) and (V) as sole or main products.

Donor–acceptor cyclopropenes are formed quantitatively or in high yield from enoldiazoacetates and enoldiazoacetamides under moderate thermal conditions. They are more versatile than their corresponding enoldiazocarbonyl compounds as carbene precursors.

This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities.

The utility of the scalable method is demonstrated by the transformation of product (VIb) into a key intermediate (XIII) for the total synthesis of the bisindole alkaloid gliocladin C (XIV).

A Rh(II)/chiral phosphoric acid cocatalyzed four-component reaction of indoles, 3-diazooxindoles, arylamines, and ethyl glyoxylate is developed, offering an extremely efficient strategy for the construction of 3,3-disubstituted 3-indol-3′-yloxindoles with excellent diastereoselectivities and high to excellent enantioselectivities. This transformation is proposed to proceed through a Mannich-type trapping of the zwitterionic intermediate generated from a metal carbene and an indole with an iminoester derived from an arylamine and a glyoxylate.

A Hg(OTf)2 catalyzed intramolecular arene 1,4-addition reaction of N-benzyl donor–acceptor cyclo-propenecarboxamides was developed to synthesize a series of [3.2.2]nonatriene derivatives. This novel reaction is also observed with silver(I) catalysts known to form metal carbene intermediates in competition with the Buchner reaction.

Donor–acceptor cyclopropenes are formed quantitatively or in high yield from enoldiazoacetates and enoldiazoacetamides under moderate thermal conditions. They are more versatile than their corresponding enoldiazocarbonyl compounds as carbene precursors.

The 3-Aryloxindoles are obtained with high regioselectivities under mild and metal-free reaction conditions.

A highly diastereo- and enantioselective four-component reaction of a diazo ketone with two molecules of anilines and ethyl glyoxylate was achieved under Rh2(OAc)4 and chiral phosphoric acid cocatalyzed conditions. This transformation proceeds through a Mannich-type trapping of the ammonium ylide generated from metal carbene and one molecule of aniline with iminoester derived from another molecule of aniline and ethyl glyoxylate. With this method, a series of chiral α,β-diamino acid derivatives were efficiently constructed in good yields and with good to excellent diastereo- and enantioselectivities.

A simple metal-free method for the synthesis of 3-aryloxindoles via Bronsted acid catalyzed aromatic C–H functionalization of electron-rich arenes with 3-diazooxindoles is developed. In the presence of a catalytic amount of TfOH, a series of 3-aryloxindoles are synthesized as single regioisomers in good to excellent yields. This transformation is proposed to proceed through acid-catalyzed protonation of 3-diazooxindoles into diazonium ions followed by Friedel–Crafts-type alkylation of arenes.

Title compounds (III) and (V) are prepared via a Rh-catalyzed reaction between either (E)-styrenyl- or alkyl-substituted 2-aminophenyl ketones (I) and (IV) and diazo compounds (II).

This new multicomponent reaction allows the selective synthesis of pyrrolidines or the corresponding linear α-amino ester derivatives by controlling the addition sequence of the substrates.

A Rh2(OAc)4-catalyzed diazo decomposition reaction of diazo esters with 2-aminophenyl ketones is reported. A series of 3-hydroxy-2,2,3-trisubstituted indolines are produced in good yields with excellent diastereoselectivities via an intramolecular aldol-type trapping of ammonium ylides with ketone units.

A series of mixed 3,3′-bisindoles were efficiently synthesized via a Rh2(OAc)4-catalyzed three-component reaction of 3-diazooxindoles with indoles and ethyl glyoxylate in high yields with excellent diastereoselectivities. The product easily underwent further synthetic transformations and could be potentially applied to the total synthesis of (±)-gliocladin C and related natural alkaloids.

A series of mixed 3,3′-bisindoles were efficiently synthesized via a Rh2(OAc)4-catalyzed three-component reaction of 3-diazooxindoles with indoles and ethyl glyoxylate in high yields with excellent diastereoselectivities. The product easily underwent further synthetic transformations and could be potentially applied to the total synthesis of (±)-gliocladin C and related natural alkaloids.

An enantioselective four-component reaction of a diazoketone, water, an aniline and ethyl glyoxylate in the presence of catalytic Rh2(OAc)4 and a chiral Bronsted acid was developed to efficiently produce β-hydroxy-α-amino acid derivatives in good yields with high diastereoselectivity and enantioselectivity.

A highly efficient three-component reaction of α-diazo ester, water and isatin was developed by using CuSO4 as the catalyst. In this reaction, water was used as both a reactant and the solvent. With this highly environmentally benign and economical protocol, a series of 3-hydroxyindolin-2-one derivatives were efficiently produced in good yields with moderate to high diastereoselectivities.

An enantioselective four-component reaction of a diazoketone, water, an aniline and ethyl glyoxylate in the presence of catalytic Rh2(OAc)4 and a chiral Bronsted acid was developed to efficiently produce β-hydroxy-α-amino acid derivatives in good yields with high diastereoselectivity and enantioselectivity.

Protein tyrosine phosphatase 1B (PTP1B) has been proposed to be an effective target for the treatment of both type II diabetes and obesity. However, no PTP1B inhibitor has come into clinic application. Herein, we report mixed 3,3′-bisindoles as novel PTP1B inhibitors with low micromole-ranged inhibitory activity. The best active compound 9f inhibited PTP1B activity with an IC50 of 2.79 µM. Meanwhile, it had low cytotoxicity and enhanced glucose uptake in vitro. Further studies demonstrated that some of these active compounds had a specific selectivity over other PTPs. Computational analysis further showed the binding mode of compound 9f with the active pocket of PTP1B. Our studies provide a novel scaffold for further development of more promising PTP1B inhibitors and potential drugs for type II diabetes and obesity.

A new strategy for the synthesis of N-alkoxycarbonyl aryl α-imino esters in the presence of dirhodium tetraacetate [Rh2(OAc)4] is reported to produce the desired compounds in high yield (up to 96%) under mild reaction conditions. The application of the synthetic method is demonstrated in enantioselective reduction and Friedel–Crafts reaction of indoles to afford the corresponding chiral arylglycines and indole derivatives, respectively, in high yield and excellent ee.

A highly diastereoselective three-component tandem 1,4-conjugate addition–cyclization reaction of diazoacetophenones with anilines and unsaturated ketoesters was developed. The reaction provides general, easy, and highly efficient access to multisubstituted pyrrolidines in good yield with high diastereoselectivity.

Imines, diazo compounds, and water undergo a rhodium/chiral Broensted acid catalyzed reaction to give the title compounds with good threo-selectivity and up to 97% enantioselectivity.

A highly efficient three-component reaction of α-diazo ester, water and isatin was developed by using CuSO4 as the catalyst. In this reaction, water was used as both a reactant and the solvent. With this highly environmentally benign and economical protocol, a series of 3-hydroxyindolin-2-one derivatives were efficiently produced in good yields with moderate to high diastereoselectivities.