Halo-perfluoroalkoxylation of gem-difluoroalkenes with short-lived alkali metal perfluoroalkoxides in triglyme.

Alkali metal alkoxides play a pivotal role in nucleophilic alkoxylation reactions, offering pathways for the synthesis of ethers, including the increasingly sought-after trifluoromethyl ethers. However, the synthesis of long-chain perfluoroalkyl ethers remains a substantial challenge in this field. Through the innovative use of triglyme to encapsulate potassium ions, we enhanced the stability of short-lived, longer-chain perfluoroalkoxy anions, thereby facilitating efficient nucleophilic perfluoroalkoxylation reactions. This method provides a new precedent for the halo-perfluoroalkoxylation of gem-difluoroalkenes and offers a versatile tool for the design of perfluoroalkyl ethers, including those containing complex moieties of heterocycles and drug molecules. We also demonstrated the utility of the resulting halo-perfluoroalkoxyl adducts through various chemical transformations to valuable diverse perfluoroalkyl ethers.

Perfluoroalkoxylation reaction via dual concurrent catalysis.

A catalytic amount of CsI enables dual concurrent activation of poorly reactive perfluoroalkoxide and alkyl halides, especially alkyl chlorides, leading to the formation of diverse perfluoroalkoxylated organic compounds. Installation of perfluoroalkoxy groups by this methodology is cost-effective, circumventing the need for over-stoichiometric cesium or silver salts. This methodology also provides high functional group compatibility and tolerance of sterically hindered substrates.

Synthesis of Enantiomerically Pure 1,2,3-Trisubstituted Cyclopropane Nucleosides Using Pd-Catalyzed Substitution via Directing Group-Mediated C(sp3)-H Activation as a Key Step.

A series of enantiomerically pure 1,2,3-trisubstituted cyclopropane nucleosides Ia-Id and IIa-IId of medicinal chemical interest was designed and synthesized. In the synthesis, a Pd-catalyzed substitution reaction via a directing group-mediated C(sp3)-H activation was effectively used to construct the 1,2,3-trisubstituted cyclopropane structure as a key step.

Entry to Chiral 1,1,2,3-Tetrasubstituted Arylcyclopropanes by Pd(II)-Catalyzed Arylation via Directing Group-Mediated C(sp3)-H Activation.

Here we report the construction of highly functionalized chiral 1,1,2,3-tetrasubstituted arylcyclopropanes of medicinal chemical importance using Pd(II)-catalyzed arylation via directing group-mediated C(sp3)-H activation. The key aspect for the effective arylation was control of the substrate conformation based on the characteristic steric and stereoelectronic features of cyclopropane by manipulating the protecting group at the hydroxyl. The arylation with good functional group tolerance is pivotal as the first entry to chiral 1,1,2,3-tetrasubstituted arylcyclopropanes with wide variety of aryl groups, including heteroaryl groups.

Total Synthesis of (+)-Goniodenin.

Goniodenin is a lipophilic polyketide originating from plant sources and which possesses a potent cytotoxic activity against cancer cell lines. The first total synthesis of (+)-goniodenin has been achieved in 23 steps from (R)-glycidol. The synthetic sequence featured a cross metathesis for the formation of the C8-C9 bond and installation of the terminal γ-butenolactone ring unit by the alkylation of α-phenylthio-γ-butyrolactone with the corresponding C3-O-triflate. The stereogenic center at C18 carbon was created by Hiyama-Fujita reduction of the corresponding ketone with high diastereoselectivity.

Development of a Sulfur-Modified Glass-Supported Pd Nanoparticle Catalyst for Suzuki-Miyaura Coupling.

A safe, facile and low-leaching (up to 0.17 ppm) sulfur-modified glass-supported palladium nanoparticle catalyst has been developed for the Suzuki-Miyaura coupling of aryl halides with aryl boronic acids. Most notably, this catalyst was highly recyclable and could be used up to 10 times without any discernible decrease in its activity.

Synthesis and GGCT Inhibitory Activity of N-Glutaryl-L-alanine Analogues.

γ-Glutamylcyclotransferase (GGCT) is an important enzyme that cleaves γ-glutamyl-amino acid in the γ-glutamyl cycle to release 5-oxoproline and amino acid. Eighteen N-acyl-L-alanine analogues including eleven new compounds have been synthesized and examined for their inhibitory activity against recombinant human GGCT protein. Simple N-glutaryl-L-alanine was found to be the most potent inhibitor for GGCT. Other N-glutaryl-L-alanine analogues having methyl and dimethyl substituents at the 2-position were moderately effective, while N-(3R-aminoglutary)-L-alanine, the substrate having an (R)-amino group at the 3-position or N-(N-methyl-3-azaglutaryl)-L-alanine, the substrate having an N-methyl substituent on the 3-azaglutaryl carbon, in constract, exhibited excellent inhibition properties.

Construction of Iterative Tetrahydrofuran Ring Units and Total Synthesis of (+)-Goniocin.

Cytotoxic acetogenin (+)-goniocin has been synthesized in 17 steps from (R)-O-tritylglycidol. The core structure of the contiguous C22-C10 threo-trans-threo-trans-threo-trans-tris-tetrahydrofuran (THF) ring involving an iterative THF-ring unit was synthesized. An iterative THF ring unit was constructed from an alkenyl-substituted THF ring in four steps including a Pd(II)-catalyzed ring-closing reaction and cross-metathesis. This method is general and allows the preparation of both trans-threo-trans- and trans-threo-cis-THF ring units flexibly.

Pd(II)-Catalyzed Alkylation of Tertiary Carbon via Directing-Group-Mediated C(sp(3))-H Activation: Synthesis of Chiral 1,1,2-Trialkyl Substituted Cyclopropanes.

A Pd(OAc)2-catalyzed alkylation reaction of the tertiary carbon of chiral cyclopropane substrates with alkyl iodides and bromides via C(sp(3))-H activation has been developed. This is an elusive example of a C-H activation-mediated alkylation of tertiary carbon to effectively construct a quaternary carbon center. The alkylation proceeded with various alkyl halides, including those of functional groups, to provide a variety of chiral cis- and trans-1,1,2,-trialkyl substituted cyclopropanes of medicinal chemical importance.

Synthesis of the Core Tricyclic Ring Domain of (-)-Schulzeine B.

A formal synthesis of (-)-schulzeine B, a marine natural alkaloid possessing potent antidiabetic activity, has been achieved. A benzo[a]quinolizidin-4-one is a common skeleton of schulzeines (A-C). (-)-Schulzeine B possesses an (S)-stereogenic center at the C-3 carbon. The chiral (3S,11bS)-3-amino-9,11-dimethoxybenzo[a]quinolizidin-4-one has been prepared efficiently from (2-bromo-3,5-dihydroxyphenyl)acetonitrile in 17 steps including (i) a dehydrative intramolecular amination catalyzed by HClO4 and (ii) a proline or boric acid catalyzed transcycloamidation reaction for the construction of the δ-lactam ring.

Palladium-nanoparticle-catalyzed 1,7-palladium migration involving C-H activation, followed by intramolecular amination: regioselective synthesis of N1-arylbenzotriazoles and an evaluation of their inhibitory activity toward indoleamine 2,3-dioxygenase.

A sulfur-modified gold-supported palladium material (SAPd) has been developed bearing palladium nanoparticles on its surface. Herein, we report for the first time the use of SAPd to affect a Pd-nanoparticle-catalyzed 1,7-Pd migration reaction for the synthesis of benzotriazoles via C-H bond activation. The resulting benzotriazoles were evaluated in terms of their inhibitory activity toward indoleamine 2,3-dioxygenase.

Ligand-free Suzuki-Miyaura coupling with sulfur-modified gold-supported palladium in the synthesis of a conformationally-restricted cyclopropane compound library with three-dimensional diversity.

A conformationally restricted privileged structure library with stereochemical diversity for a "fragment growth" methodology comprising 90 compounds was designed and systematically and efficiently synthesized using sulfur-modified Au-supported Pd (SAPd)-catalyzed ligand-free Suzuki-Miyaura coupling of vinyl iodide promoted by microwave and subsequent amidation in liquid-phase combinatorial chemistry as key reactions. Evaluation of the compounds with a 20-kinase panel indicated the usefulness of this "fragment growth" methodology for finding hit library compounds for fragment-based drug discovery.

Palladium-catalyzed amination of unprotected five-membered heterocyclic bromides.

An efficient method for the palladium-catalyzed amination of unprotected bromoimidazoles and bromopyrazoles is presented. The transformation is facilitated by the use of our newly developed Pd precatalyst based on the bulky biarylphosphine ligand tBuBrettPhos (L4). The mild reaction conditions employed allow for the preparation of a broad scope of aminoimidazoles and aminopyrazoles in moderate to excellent yields.

Palladium-catalyzed arylation of cyclopropanes via directing group-mediated C(sp3)-H bond activation to construct quaternary carbon centers: synthesis of cis- and trans-1,1,2-trisubstituted chiral cyclopropanes.

Pd(II)-catalyzed tertiary C(sp(3))-H arylation of cyclopropanes via directing group-mediated C-H activation for the construction of a chiral quaternary carbon center on cyclopropanes using aryl iodides as a coupling partner is reported. The arylation had a wide substrate scope and good functional group tolerance, including heteroaryl iodides, to provide various chiral arylcyclopropanes with the cis- and trans-1,1,2-trisubstituted structures.

Preparation of chiral bromomethylenecyclopropane and its use in Suzuki-Miyaura coupling: synthesis of the arylmethyl-(Z)-cyclopropane structure core.

A preparative method for an optically active bromomethylenecyclopropane unit and its practical conversion to (Z)-cyclopropane-containing chiral compounds via Suzuki-Miyaura coupling were established.

An Improved Synthesis of BrettPhos and RockPhos-Type Biarylphosphine Ligands.

Improved processes for the preparation of biphenyl-based phosphine ligands t-BuBrettPhos, RockPhos, and BrettPhos are presented. The new methods, featuring the use of Grignard reagents and catalytic amounts of copper, are superior to the previous methods, which require the use of t-butyllithium and stoichiometric amounts of copper. Specifically, the use of less dangerous reagents provides a safer process, while the use of catalytic amounts of copper allows for the isolation of pure products in high yield. These improvements are particularly significant for the large scale preparation of these ligands.

Sulfur modification of Au via treatment with Piranha solution provides low-Pd releasing and recyclable Pd material, SAPd.

We have found in the SR-HXPS measurement of Piranha-treated Au(111)/mica that the gold surface underwent sulfur modification during this treatment, which was believed to have only removed impurities from the gold surface. We also successfully developed a practical Pd material, SAPd, whose Pd was immobilized on sulfur-modified Au. With the lowest Pd-releasing levels and high recyclability, this is one of the best Pd materials thus far developed. Because it leaches extremely low levels of Pd into reaction mixtures, removal of the residual Pd is unnecessary using SAPd, even in syntheses involving pharmaceutical ingredients.

Color modulation for intramolecular charge-transfer-induced chemiluminescence of 1,2-dioxetanes.

Dioxetanes bearing an aromatic electron donor decompose with an accompanying emission of light by an intramolecular charge-transfer-induced chemiluminescence (CTICL) mechanism. The color of the chemiluminescence from CTICL-active aryl-substituted dioxetanes is controlled by the design of the aromatic moiety and its substitution pattern, and the substituent on the carbon of the dioxetane ring. In addition to these color modulations, a change in the conformation of dioxetanes bearing a biaryl group was also found to cause a change in the color of CTICL in the coordination sphere of a crown ether complex. This new color modulation system was further developed for optically active dioxetanes bearing 2-hydroxy-1,1'-binaphthyl, the CTICL of which took place under the chiral recognition of optically active crown ether complexes. The spectra of the chemiluminescence from biaryl-type dioxetanes did not coincide with the fluorescence spectrum from the authentic emitter in the coordination sphere, but they did coincide with each other in a completely homogeneous system. This finding suggests that the emitter of CTICL possesses a transient structure, which retains the afterimage of the conformation of the dioxetane.