Synthesis of Poly(δ-caprolactone) via Bis(phenolate) Rare-Earth Metal Complexes Mediated Ring-Opening Polymerization and Its Chemical Recycling.

New amine-amino-bis(phenolate) ligands (H2LtBu and H2LCl) with a cyclic tertiary amine (pyrrolidine) as a side arm and tBu or Cl group on the phenolate ring have been prepared. The alkane elimination reaction between these free ligands and rare-earth tris(alkyl)s Ln(CH2SiMe3)3(THF)2 afforded the corresponding silylalkyl complexes LtBuLnCH2SiMe3(THF) (Ln = Y (1), Lu (2)) and LClYCH2SiMe3(THF) (3), where the solid-state structure of complex 1 was unambiguously confirmed by X-ray diffraction (XRD) analysis. These rare-earth metal complexes have been utilized as catalysts for the ring-opening polymerization (ROP) of biobased δ-caprolactone (δCL), either in the absence or presence of alcohols, to give poly(δ-caprolactone) (PδCL) with controlled molecular weight and narrow distribution (D < 1.2). The polymerization kinetics of δCL in toluene with yttrium complexes 1 and 3 were investigated. Oligomers prepared with complex 3 alone and the 3/PhCHMeOH binary catalyst system were well characterized with 1H NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). Moreover, chemical recycling of the resultant PδCL was achieved with high yield in a solution at ambient temperature (>92%) or in bulk at 130 °C (>82%) by using commercial KOtBu as a promotor.

LGALS1 regulates cell adhesion to promote the progression of ovarian cancer.

The present study aimed to explore the significance and molecular mechanisms of galectin-1 (LGALS1) in ovarian cancer (OC). Using the Gene Expression Omnibus database and The Cancer Genome Atlas database, the results of the present study demonstrated that LGALS1 mRNA expression was markedly increased in OC and associated with advanced tumor, lymphatic metastasis and residual lesions. In Kaplan-Meier analysis, patients who expressed LGALS1 highly had a poor prognosis. Furthermore, using The Cancer Genome Atlas database, differentially expressed genes that are potentially regulated by LGALS1 in OC were determined. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis were used to build a biological network of upregulated differentially expressed genes. The results of the enrichment analysis revealed that the upregulated differentially expressed genes were primarily associated with 'ECM-receptor interaction', 'cell-matrix adhesion' and 'focal adhesion', which are closely associated with the metastasis of cancer cells. Subsequently, cell adhesion was selected for further analysis. The results demonstrated that LGALS1 was co-expressed with the candidate genes. Subsequently, the elevated expression levels of candidate genes were verified in OC tissues, and survival analysis indicated that high expression of candidate genes was associated with shortened overall survival of patients with OC. In the present study, OC samples were also collected to verify the high protein expression levels of LGALS1 and fibronectin 1. The results of the present study highlighted that LGALS1 may regulate cell adhesion and participate in the development of OC. Therefore, LGALS1 exhibits potential as a therapeutic target in OC.

Nickel-Catalyzed Reductive Csp2-Csp3 Cross Coupling Using Phosphonium Salts.

A nickel-catalyzed reductive cross coupling with phosphonium salts and allylic C(sp3)-O bond electrophiles, which granted direct construction of the C(sp2)-C(sp3) bond, is successfully developed. The protocol features broad substrate scope, high-functional-group tolerance, and heterocycle compatibility. Notably, the much more challenging reductive cross coupling with heterocyclic thiazolylphosphonium salts has also been accomplished for the first time.

One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence.

We have developed a one-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed [3+2] annulation of oxabicyclic alkenes followed by a ring-opening/dehydration sequence in good to excellent yields. With the use of 2-(1-methylhydrazinyl)pyridine (MHP), first explored by our group as the bidentate directing group in C-H functionalization of benzoic hydrazides, the new reaction sequence proceeded smoothly and tolerated a wide range of functional groups, featuring facile scalability. Notably, oxygen served as the green oxidant in the reaction system. Careful tuning of the reaction parameters assured the direct synthesis of benzo[b]fluorenones through aromatization of the dihydroepoxybenzofluorenone intermediate.

A facile method for the synthesis of 2-(3-hydroxy-1-adamantyl)-2-oxoacetic acid and it's optimization.

2-(3-hydroxy-1-adamantyl)-2-oxoacetic acid (IV), a key intermediate of saxagliptin for type 2 diabetes mellitus (T2DM), was prepared from 1-adamantanecarboxylic acid(I) via oxidation by potassium permanganate(KMnO4) to afford 3-hydroxy-1-adamantanecarboxylic acid (II), which was treated with a one-pot method to give 1-acetyl-3-hydroxyadamantane (III) followed by oxidation. Some key steps were optimized and the overall yield was about 51%.

Copper-catalyzed decarboxylative propargylation/hydroamination reactions: access to C3 ß-ketoester-functionalized indoles.

A copper-catalyzed reaction of ethynyl benzoxazinanones with readily accessible ß-ketoesters via a decarboxylative propargylation/hydroamination sequence has been developed. This protocol furnished a diverse range of C3 ß-ketoester-functionalized indoles in good to excellent yields.

A 2-(1-methylhydrazinyl)pyridine-directed C-H functionalization/spirocyclization cascade: facile access to spirosuccinimide derivatives.

A cobalt-catalyzed oxidative coupling of benzoic hydrazides with maleimides by utilizing 2-(1-methylhydrazinyl)pyridine as a bidentate directing group has been developed. This C-H functionalization/spirocyclization cascade protocol shows high efficiency and remarkable functional group tolerance, and the ubiquitous spirosuccinimides were obtained in good to excellent yields with high regioselectivity. This strategy also provides a novel and efficient access to diverse symmetric and unsymmetrical bisspirosuccinimides.

Collective Total Synthesis of (-)-Lundurines A-C.

A collective asymmetric total synthesis of lundurines A-C using l-pyroglutamic acid derived from the chiral pool is described. The key steps include a tandem reductive amination/lactamization sequence to introduce the pyrrolidinone ring, a palladium-catalyzed intramolecular direct C-H vinylation of indole to construct the crucial polyhydroazocine ring, and a Lewis acid promoted formal [3 + 2] cycloaddition/N2 extrusion process to install the polysubstituted cyclopropyl ring.

Divergent Total Syntheses of (-)-Daphnilongeranin†B and (-)-Daphenylline.

(-)-Daphnilongeranin B and (-)-daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (-)-daphnilongeranin B and a bioinspired synthesis of (-)-daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late-stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.

Organocatalytic Synthesis of 4-Aryl-1,2,3,4-tetrahydropyridines from Morita-Baylis-Hillman Carbonates through a One-Pot Three-Component Cyclization.

An efficient DABCO-catalyzed three-component formal [3 + 2 + 1] annulation, involving a Morita-Baylis-Hillman carbonate, a 1,3-ketoester, and a primary amine, leading to one-pot synthesis of substituted 4-aryl-1,2,3,4-tetrahydropyridines, has been developed. The densely functionalized products were generally obtained in good to excellent yields under mild conditions. The structures including the relative stereoconfigurations of the representative products were confirmed by X-ray diffraction analysis.

2-(1-Methylhydrazinyl)pyridine as a reductively removable directing group in a cobalt-catalyzed C(sp2)-H bond alkenylation/annulation cascade.

We describe a new application of 2-(1-methylhydrazinyl)pyridine as a bidentate directing group to directing cobalt-catalyzed C(sp2)-H alkenylation/annulation of the corresponding benzoic hydrazides to form an isoquinoline backbone, via reacting with a terminal or internal alkyne followed by annulation. The reaction shows a broad substrate scope with the products obtained in good to excellent yields and high regioselectivity. Moreover, the directing group can be reductively removed in one step under mild conditions.

Blue-light-promoted carbon-carbon double bond isomerization and its application in the syntheses of quinolines.

A blue-light-promoted carbon-carbon double bond isomerization in the absence of any photoredox catalyst is reported. It provides rapid access to a series of quinolines in good to excellent yields under simple aerobic conditions. The protocol is direct, catalyst-free and operationally convenient.

Asymmetric Total Synthesis of (-)-Aspidophylline A.

An asymmetric total synthesis of (-)-aspidophylline A has been accomplished. The key transformations include an asymmetric hydride transfer hydrogenation of an α,ß-acetylenic ketone and a cationic gold(I)-catalyzed 6-exo-dig cyclization involving an alkynylindole/aminal formation cascade, which enables stereoselective establishment of the requisite quaternary carbon center.

Formal Synthesis of (±)-Aplykurodinone-1 through a Hetero-Pauson-Khand Cycloaddition Approach.

The tricyclic intermediate 2 has been synthesized in eight steps from known compound 6 in 20% overall yield. As such, this constitutes a highly efficient formal synthesis of (±)-aplykurodinone-1. This synthesis features a unique, one-pot, intramolecular hetero-Pauson-Khand reaction (h-PKR)/desilylation sequence to expeditiously construct the tricyclic framework, providing valuable insights for expanding the scope and boundaries of h-PKR.

Total Synthesis of the Diterpenoid (+)-Harringtonolide.

Described herein is the first asymmetric total synthesis of (+)-harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels-Alder reaction and a rhodium-complex-catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation.

Decarboxylative Csp(3)-Csp(3) coupling for benzylation of unstable ketone enolates: synthesis of p-(acylethyl)phenols.

A new decarboxylative Csp(3)-Csp(3) coupling approach for the benzylation of ketone enolates has been developed. A variety of raspberry ketone derivatives were conveniently synthesized in good to excellent yields under mild conditions. A crossover reaction shed light on the mechanism of this tandem reaction.

Correction: Decarboxylative Csp3-Csp3 coupling for benzylation of unstable ketone enolates: synthesis of p-(acylethyl)phenols.

Correction for 'Decarboxylative Csp3-Csp3 coupling for benzylation of unstable ketone enolates: synthesis of p-(acylethyl)phenols' by Sasa Wang et al., Chem. Commun., 2016, 52, 9454-9457.

Synthesis of Polysubstituted Pyridines via a One-Pot Metal-Free Strategy.

An efficient strategy for the one-pot synthesis of polysubstituted pyridines via a cascade reaction from aldehydes, phosphorus ylides, and propargyl azide is reported. The reaction sequence involves a Wittig reaction, a Staudinger reaction, an aza-Wittig reaction, a 6π-3-azatriene electrocyclization, and a 1,3-H shift. This protocol provides quick access to the polysubstituted pyridines from readily available substrates in good to excellent yields.

A One-Pot Synthesis of Dibenzofurans from 6-Diazo-2-cyclohexenones.

A novel and efficient protocol for the rapid construction of dibenzofuran motifs from 6-diazo-2-cyclohexenone and ortho-haloiodobenzene has been developed. The process involves one-pot Pd-catalyzed cross-coupling/aromatization and Cu-catalyzed Ullmann coupling.

Rapid construction of [5-6-7] tricyclic ring skeleton of Calyciphylline alkaloid daphnilongeranin B.

A concise photochemical [2 + 2] cycloaddition-Grob fragmentation sequence sets the common tricyclic ring skeletons of the Calyciphylline A-type alkaloids, particularly those in daphnilongeranins, daphniyunnines, and daphniglaucins.