Highly Regio- and Diastereoselective Synthesis of 6,7-Dihydro-4H-furo[3,4-c]pyran Derivatives through Pd-Catalyzed Formal (3 + 3) Allylic Cycloaddition of 2-Butene-1,4-diols with 2-(1-Alkynyl)-2-alken-1-ones.

A highly efficient synthesis of 7-vinyl-6,7-dihydro-4H-furo[3,4-c]pyran derivatives from 2-butene-1,4-diols and 2-(1-alkynyl)-2-alken-1-ones has been achieved with high regio- and diastereoselectivity (dr > 20:1) by Pd-catalyzed tandem heterocyclization/cross-coupling. The π-allyl palladium species Int II generated from 2-butene-1,4-diol by direct cleavage of the C-OH bond is the key to the success in this formal (3 + 3) cycloaddition reaction.

Access to N-Aryl (Iso)quinolones via Aryne-Induced Three-Component Coupling Reaction.

N-Aryl (iso)quinolones are of increasing interest in material and medicinal chemistry, although general routes for their provision remain underexplored, especially when compared with its N-alkyl counterparts. Herein, we report a modular and transition-metal-free, aryne-induced three-component coupling protocol that allows the facile synthesis of structurally diverse N-aryl (iso)quinolones from readily accessible halo-(iso)quinolines in the presence of water. Preliminary results highlight the applicability of our method through scale-up synthesis, downstream derivatization, and flexible synthesis involving other types of aryne precursors.

[Research progress in drugs targeting 5-lipoxygenase for age-related diseases].

With the acceleration of aging society, delaying aging or promoting healthy aging has become a major demand for human health. 5-Lipoxygenase (5-LOX) is a key enzyme catalyzing arachidonic acid into leukotrienes (LTs), which is a potent mediator of the inflammatory response. Previous studies showed that abnormal activation of 5-LOX and overproduction of LTs are closely related to the occurrence and development of aging-related inflammatory diseases. Therefore, inhibiting 5-LOX activation is a possibly potential strategy for treating age-related diseases. In this paper, the latest research progress in 5-LOX activation, 5-LOX in mediating aging-related diseases and its small molecule inhibitors is briefly reviewed to provide scientific theoretical basis and new ideas for the prevention and treatment of aging-related inflammatory diseases.

Synthesis of 3-aminoindenes and cis-1-aminoindanes by Zn(OTf)2-catalyzed cyclization of o-alkynylbenzaldehydes with tertiary alkyl primary amines.

Using Zn(OTf)2 as catalyst, a highly regio- and chemo-selective cyclocarboamination of o-alkynylbenzaldehydes with tertiary alkyl primary amines was realized to access 3-aminoindenes with different substitution patterns from previously reported methods. The full reduction of the iminoindenone intermediates affords cis-1-amino-2-arylindanes with excellent diastereoselectivity. Mechanistically, the reaction involves the rearrangement of 1-amino-3-arylidene-isoindolines and isomerization of 1-aminoindenes to 3-aminoindenes.

Synthesis of 3-aminotetrahydro-1H-carbazols by visible-light photocatalyzed cycloaddition of cyclopropylanilines with 2-alkenylarylisocyanides.

A visible-light-induced cycloaddition between 2-alkenylarylisocyanides and cyclopropylanilines is reported. This cascade radical reaction constructs two new C-C bonds and two rings to afford 3-aminotetrahydro-1H-carbazols with high atom and step economy. The mechanism is rationalized as involving sequential distonic radical cation formation/isocyanide insertion/5-exo-trig cyclization/intramolecular iminium ion addition/tautomerization.

Design, synthesis and biological evaluation of novel nitric oxide donors with antioxidative activity.

Reactive oxygen species (ROS) are the primary cause of organic nitrate drug tolerance and endothelial dysfunction. In order to scavenge the ROS and maintain the therapeutic effect of nitrates, we designed and synthesized ten new types of dual-acting nitrate molecules by combining NIT-type nitroxides and 5-ISMN. These included two types of novel epimeric nitroxide-nitrate conjugates (15(S) and 15(R)), which had pharmacophore connections. We also synthesized 8 NIT radicals without 5-ISMN in order to compare the activities of these novel nitric oxide donors. Several dual-acting nitroxide-based nitrate conjugates showed the ability to release NO and cause anti-oxidant effects in human umbilical vein endothelial cells. Among these conjugates, 15(S) showed the most prominent pro-vasodilative effect. In angiotensin II infusion-induced hypertensive mice, 15(S) treatment for 4 weeks decreased both the systolic and diastolic blood pressures and ameliorated the vascular endothelial and smooth muscle functions of isolated thoracic aortas. In addition, the vascular structure of the mice was restored and their vascular oxidative stress was decreased. The results suggest that these novel nitric oxide donors can be used as potential drugs in the treatment of vascular diseases. Therefore, the strategy of using a combination of antioxidants and NO-donors can be a promising way to develop novel organic nitrate drugs for future use in combating disease.

Transition-metal-free approaches to 2,3-diarylated indenones from 2-alkynylbenzaldehydes and phenols with tunable selectivity.

The first transition-metal-free regioselective synthesis of 2,3-diarylindenones via tandem annulation of 2-alkynylbenzaldehydes with phenols is described. Two different modes of reaction controlled by electronic effects and temperature furnished either "non-rearranged" or "rearranged" indenones in high selectivity.

Cleavage and Reassembly of the C═O Bond of 2-Alkynylbenzaldehydes: A Metal-Free Access to Inden-1-ones.

A metal-free approach to inden-1-ones from 2-alkynylbenzaldehydes mediated by pyrrolidine has been developed. The reaction proceeds under mild conditions in a step- and atom-economy process by cleaving the C═O bond and constructing new C-C as well as C═O bonds. Oxygen-18 and deuterium labeling experiments revealed an aza-Petasis-Ferrier rearrangement of an intermediate 1-amino-3-methylene-dihydroisobenzofuran.

Palladium-Catalyzed Three-Component Carbocarbonation of Arynes: Expeditious Synthesis of o-Alkylated Arylacrylates and Stilbenes.

A palladium-catalyzed multicomponent reaction involving olefin-tethered aryl iodides, arynes, and electrophilic alkenes has been developed for straightforward synthesis of o-alkylated arylacrylates and stilbenes through tandem intramolecular Heck cyclization/aryne dicarbofunctionalization.

Palladium-catalyzed Ugi-type reaction of 2-iodoanilines with isocyanides and carboxylic acids affording N-acyl anthranilamides.

The first palladium-catalyzed Ugi-type multicomponent reaction for the synthesis of N-acyl anthranilamides from isocyanides, 2-iodoanilines and carboxylic acids has been developed. This method provides expeditious and highly efficient access to structurally diverse N-acyl anthranilamides from readily available starting materials with good functional group compatibility. The utility of this method has been demonstrated by the late stage functionalization of two commercial drugs: Flurbiprofen and Loxoprofen.

Ligand-Controlled Palladium-Catalyzed Chemoselective Multicomponent Reaction of Olefin-Tethered Aryl Halides, Isocyanides, and Carboxylic Acids: Diversified Synthesis of Imides.

The first palladium-catalyzed, ligand-controlled chemoselective synthesis of imides has been achieved. An orthogonal set of conditions has been developed for multicomponent reaction of various olefin-tethered aryl iodides, isocyanides, and carboxylic acids. Alkylimides ("cyclization on" products) via arylimidation of tethered unactivated alkenes and aryl imides ("cyclization off" products) via direct imidation of aryl iodides were obtained in good to excellent yields with good to excellent selectivity. Computational studies were performed to gain insight into the origin of the high levels of chemoselectivity observed.

Visible-Light-Induced Decarboxylative Cyclization of 2-Alkenylarylisocyanides with α-Oxocarboxylic Acids: Access to 2-Acylindoles.

An efficient and practical protocol for visible-light-induced decarboxylative cyclization of 2-alkenylarylisocyanides with α-oxocarboxylic acids has been developed, which afforded a broad range of 2-acylindoles in moderate to good yields. The reaction proceeds through a cascade of acyl radical addition/cyclization reactions under irradiation of an Ir3+ photoredox catalyst without external oxidants and features simple operation, scalability, a broad substrate scope, and good functional group tolerance.

Silver-Catalyzed Decarboxylative Allylation of Difluoroarylacetic Acids with Allyl Sulfones in Water.

A practical silver-catalyzed decarboxylative allylation of α,α-difluoroarylacetic acids with allyl sulfones is described, which provides a variety of ß,ß-difluorinated alkenes in good yields. Notably, the reaction proceeds smoothly in water with good functional group tolerance. The practicality and synthetic value of this process was demonstrated by scaled-up experiment and elaboration of the products via reduction or Heck reaction. Primary mechanism investigations suggest that a radical process might be involved.

Synthesis of imides via palladium-catalyzed three-component coupling of aryl halides, isocyanides and carboxylic acids.

A palladium-catalyzed three-component synthesis of acyclic imides from feedstock aryl halides, carboxylic acids and isocyanides through the intermediacy of isoimides has been developed. The key to the success of this approach was controlled isocyanide slow addition and organic/aqueous biphasic conditions. This transition-metal-catalyzed approach features readily available starting materials, atom- and step-economy, good functional group compatibility and gram-scale synthetic capability. Utilization of this new method is illustrated in the late-stage functionalization of drugs Carprofen, Loxoprofen and Flurbiprofen. This strategy has also been successfully applied in the synthesis of cyclic imides including phthalimide, homophthalimide, and 2H-2-benzazepine-1,3-dione derivatives.

Regio- and Stereoselective Electrophilic Cyclization Approach for the Protecting-Group-Free Synthesis of Alkaloids Lennoxamine, Chilenine, Fumaridine, 8-Oxypseudoplamatine, and 2- O-(Methyloxy)fagaronine.

A unified strategy for protecting-group-free synthesis of alkaloids lennoxamine, chilenine, fumaridine, 8-oxypseudoplamatine, and 2- O-(methyloxy)fagaronine is reported. The core isoindolin-1-one and isoquinolin-1-one structures were built by a silver-catalyzed regio- and stereoselective cyclization of methyl 2-alkynylbenzimidates. The regioselectivity of cyclization was achieved by utilizing the intrinsic functionality of alkaloids.

Highly Selective Synthesis of Dihydrobenzo[d]isoxazoles and Dihydrobenzo[d]oxazoles from Oximes and Arynes via in Situ Generation of Nitrones.

An efficient method for the synthesis of dihydrobenzo[d]isoxazoles and dihydrobenzo[d]oxazoles bearing a quaternary carbon center has been developed. The reaction involves generation of a ketonitrone intermediate in situ from a ketoxime and an aryne. A novel thermal rearrangement of the dihydrobenzo[d]isoxazole products to the corresponding dihydrobenzo[d]oxazoles has been observed. These transformations tolerate a variety of functional groups and offer a rapid and efficient way to diverse dihydrobenzo[d]isoxazoles and dihydrobenzo[d]oxazoles under mild transition-metal-free conditions.

Palladium-Catalyzed Domino Heck/Aryne Carbopalladation/C-H Functionalization: Synthesis of Heterocycle-Fused 9,10-Dihydrophenanthrenes.

A novel palladium-catalyzed domino Heck/aryne carbopalladation/C-H functionalization reaction using in situ generated arynes has been developed in which three new C-C bonds and a carbon quaternary center are formed. This methodology affords moderate to excellent yields of heterocycle-fused 9,10-dihydrophenanthrenes.

Palladium-catalyzed domino Heck/intermolecular cross-coupling: efficient synthesis of 4-alkylated isoquinoline derivatives.

A highly efficient Pd-catalyzed Heck-type cascade process with 2-(1-alkynyl)benzaldimines has been developed, which provides access to a broad range of 4-alkylated isoquinoline derivatives in moderate to good yields. The σ-alkylpalladium(ii) intermediate in the Heck reaction activates alkynes toward intramolecular nucleophilic attack. This is the first example of a σ-alkylpalladium(ii) intermediate promoting the cyclization of alkynes containing a proximate nucleophilic center.

Synthesis of 9,10-Phenanthrenes via Palladium-Catalyzed Aryne Annulation by o-Halostyrenes and Formal Synthesis of (±)-Tylophorine.

A novel palladium-catalyzed annulation reaction of in situ generated arynes and o-halostyrenes has been developed. This methodology affords moderate to excellent yields of substituted phenanthrenes and is tolerant of a variety of functional groups such as nitrile, ester, amide, and ketone. This annulation chemistry has been successfully applied to the formal total synthesis of a biologically active alkaloid (±)-tylophorine.

One-pot, regiospecific assembly of (E)-benzamidines from δ- and γ-amino acids via an intramolecular aminoquinazolinone rearrangement.

The efficient generation of novel, N-linked benzamidines resulting from a regiospecific rearrangement of quinazolinones is described. This methodology study explored reaction parameters including the effect of changing solvent and temperature, as well as varying electronic substituents on the structural core. The transformation was extensively optimized in terms of reaction conditions and scope, resulting in a protocol that consistently affords diversely functionalized amidines in high yield. The process permits regional structural derivatization that was previously inaccessible, and the multistep process was also reduced to a telescoped, five-step sequence that efficiently affords pharmacologically unique (E)-benzamidoamidines from N-BOC protected γ- and δ-amino acids.