α-Alkylation and Asymmetric Transfer Hydrogenation of Tetralone via Hydrogen Borrowing and Dynamic Kinetic Resolution Strategy Using a Single Iridium(III) Complex.

Here we present a novel strategy for the synthesis of enantiomerically enriched tetrahydronaphthalen-1-ols. The reaction proceeds via an alkylation (via hydrogen borrowing) and ammonium formate-mediated asymmetric transfer hydrogenation (via dynamic kinetic resolution), giving alkylated tetralols in high yields and good enantio- and diastereoselectivity across a diverse range of both alcohol and tetralone substrates. Additionally, these products were successfully derivatized to several complex molecules, demonstrating the utility of the tetrahydronaphthalen-1-ol.

Controlled synthesis of polycarbonate diols and their polylactide block copolymers using amino-bis(phenolate) chromium hydroxide complexes.

A diamine-bis(phenolate) chromium(III) complex, CrOH[L] ([L] = dimethylaminoethylamino-N,N-bis(2-methylene-4,6-tert-butylphenolate)), 2, in the presence of tetrabutylammonium hydroxide effectively copolymerizes CO2 and cyclohexene oxide (CHO) into a polycarbonate diol. The resultant low molar mass (6.3 kg mol-1) diol is used to initiate ring-opening polymerization of rac-lactide with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) giving ABA-type block copolymers with good molar mass control through varying rac-LA-to-diol loadings and with narrow dispersities. As the degree of rac-LA incorporation increases, the glass transition temperatures (Tg) are found to decrease, whereas decomposition temperatures (Td) increase. (Diphenylphosphonimido)triphenylphosphorane (Ph2P(O)NPPh3) was used as a neutral nucleophilic cocatalyst with 2, giving phosphorus-containing polycarbonates with an Mn value of 28.5 kg mol-1, a dispersity of 1.13, a Tg value of 110 °C and a Td value of over 300 °C. A related Cr(III) complex (4) having a methoxyethyl pendent group rather than a dimethylaminoethyl group was structurally characterized as a hydroxide-bridged dimer.

Development of a Crystallization-Induced Diastereomer Transformation of Oxime Isomers for the Asymmetric Synthesis of (1S,6R)-3,9-Diazabicyclo[4.2.1]nonane.

Herein we report a practical crystallization-induced diastereomer transformation (CIDT) of oxime isomers for the scalable asymmetric synthesis of the bicyclic diamine (1S,6R)-3,9-diazabicyclo[4.2.1]nonane derivative that serves as a valuable building block in medicinal chemistry. The developed approach utilizes (S)-phenylethylamine as a chiral auxiliary handle for CIDT, and the starting nortropinone derivative is prepared in one step from commercially available materials. The resulting E-oxime is subjected to a stereospecific Beckmann rearrangement, followed by reduction of the resulting lactam with LiAlH4 to afford the monoprotected (1S,6R)-3,9-diazabicyclo[4.2.1]nonane derivative. The development of the CIDT and understanding of the mechanistic implications leading to the high selectivity are reported.

A Stereocontrolled Synthesis of a Phosphorothioate Cyclic Dinucleotide-Based STING Agonist.

We describe a stereodefined synthesis of the newly identified non-natural phosphorothioate cyclic dinucleotide (CDN) STING agonist, BMT-390025. The new route avoids the low-yielding racemic approach using P(III)-based reagents, and the stereospecific assembly of the phosphorothioate linkages are forged via the recently invented P(V)-based platform of the so-called PSI (Ψ) reagent system. This P(V) approach allows for the complete control of chirality of the P-based linkages and enabled conclusive evidence of the absolute configuration. The new approach offers robust procedures for preparing the stereodefined CDN in eight steps starting from advanced nucelosides, with late-stage direct drop isolations and telescoped steps enabling an efficient scale-up that proceeded in an overall 15% yield to produce multigram amounts of the CDN.

Discovery of BMS-753426: A Potent Orally Bioavailable Antagonist of CC Chemokine Receptor 2.

To improve the metabolic stability profile of BMS-741672 (1a), we undertook a structure-activity relationship study in our trisubstituted cyclohexylamine series. This ultimately led to the identification of 2d (BMS-753426) as a potent and orally bioavailable antagonist of CCR2. Compared to previous clinical candidate 1a, the tert-butyl amine 2d showed significant improvements in pharmacokinetic properties, with lower clearance and higher oral bioavailability. Furthermore, compound 2d exhibited improved affinity for CCR5 and good activity in models of both monocyte migration and multiple sclerosis in the hCCR2 knock-in mouse. The synthesis of 2d was facilitated by the development of a simplified approach to key intermediate (4R)-9b that deployed a stereoselective reductive amination which may prove to be of general interest.

Photocatalytic Dearomative Intermolecular [2 + 2] Cycloaddition of Heterocycles for Building Molecular Complexity.

Indole and indoline rings are important pharmacophoric scaffolds found in marketed drugs, agrochemicals, and biologically active molecules. The [2 + 2] cycloaddition reaction is a versatile strategy for constructing architecturally interesting, sp3-rich cyclobutane-fused scaffolds with potential applications in drug discovery programs. A general platform for visible-light mediated intermolecular [2 + 2] cycloaddition of indoles with alkenes has been realized. A substrate-based screening approach led to the discovery of tert-butyloxycarbonyl (Boc)-protected indole-2-carboxyesters as suitable motifs for the intermolecular [2 + 2] cycloaddition reaction. Significantly, the reaction proceeds in good yield with a wide variety of both activated and unactivated alkenes, including those containing free amines and alcohols, and the transformation exhibits excellent regio- and diastereoselectivity. Moreover, the scope of the indole substrate is very broad, extending to previously unexplored azaindole heterocycles that collectively afford fused cyclobutane containing scaffolds that offer unique properties with functional handles and vectors suitable for further derivatization. DFT computational studies provide insights into the mechanism of this [2 + 2] cycloaddition, which is initiated by a triplet-triplet energy transfer process. The photocatalytic reaction was successfully performed on a 100 g scale to provide the dihydroindole analog.

Synthesis of 1-(tert-Butyl) 4-Methyl (1R,2S,4R)-2-Methylcyclohexane-1,4-dicarboxylate from Hagemann's tert-Butyl Ester for an Improved Synthesis of BMS-986251.

We describe an efficient synthetic route to differentially protected diester, 1-(tert-butyl) 4-methyl (1R,2S,4R)-2-methylcyclohexane-1,4-dicarboxylate (+)-1, via palladium-catalyzed methoxycarbonylation of an enol triflate derived from a Hagemann's ester derivative followed by a stereoselective Crabtree hydrogenation. Diester 1 is a novel chiral synthon useful in drug discovery and was instrumental in the generation of useful SAR during a RORγt inverse agonist program. In addition, we describe a second-generation synthesis of the clinical candidate BMS-986251, using diester 1 as a critical component.

Mixed-Valence Superstructure Assembled from a Mixed-Valence Host-Guest Complex.

Herein, we report an unprecedented mixed-valence crystal superstructure that consists of a 2:1 host-guest complex [MV⊂(CBPQT)2]2/3+ [MV = methyl viologen, CBPQT = cyclobis(paraquat- p-phenylene)]. One electron is distributed statistically between three [MV⊂(CBPQT)2]•+ composed of a total of 15 viologen units. The mixed-valence state is validated by single-crystal X-ray crystallography, which supports an empirical formula of [MV⊂(CBPQT)2]3·(PF6)2 for the body-centered cubic superstructure. Electron paramagnetic resonance provides further evidence of electron delocalization. Quantum chemistry calculations confirm the mixed-valence state in the crystal superstructure. Our findings demonstrate that precise tuning of the redox states in host-guest systems can lead to a promising supramolecular strategy for achieving long-range electron delocalization in solid-state devices.

Aqua-chlorido-(2-{[6-(di-methyl-amino)-pyrimidin-4-yl]sulfan-yl}pyrimidine-4,6-di-amine)-copper(II) chloride hydrate.

A copper(II) complex of the non-symmetric bidentate ligand 2-{[6-(di-methyl-amino)-pyrimidin-4-yl]sulfan-yl}pyrimidine-4,6-di-amine (L1) is reported. The single-crystal X-ray structure of aqua-[aqua/chlorido-(0.49/0.51)](2-{[6-(di-methyl-amino)-pyrimidin-4-yl]sulfan-yl}pyrimidine-4,6-di-amine)-copper(II) 0.49-chloride 1.51-hydrate, [CuCl1.51(C10H13N7S)(H2O)1.49]Cl0.49·1.51H2O or [(L1)Cl1.51(H2O)1.49Cu]0.49Cl·1.51H2O, exhibits distorted square-pyramidal geometry around the metal centre, with disorder in the axial position, occupied by chloride or water. The six-membered metal-chelate ring is in a boat conformation, and short inter-molecular S⋯S inter-actions are observed. In addition to its capacity for bidentate metal coordination, the ligand has the ability to engage in further supra-molecular inter-actions as both a hydrogen-bond donor and acceptor, and multiple inter-actions with lattice solvent water mol-ecules are present in the reported structure.

Tricaesium citrate monohydrate, Cs3C6H5O7·H2O: crystal structure and DFT comparison.

The crystal structure of tricaesium citrate monohydrate, 3Cs+·C6H5O73-·H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. This compound is isostructural to the K+ and Rb+ compounds with the same formula. The three independent Cs cations are eight-, eight-, and seven-coordinate, with bond-valence sums of 0.91, 1.22, and 1.12 valence units. The coordination polyhedra link into a three-dimensional framework. The hy-droxy group forms the usual S(5) hydrogen bond with the central carboxyl-ate group, and the water mol-ecule acts as a donor in two strong hydrogen bonds.

Crystal structure of dicesium hydrogen citrate from laboratory single-crystal and powder X-ray diffraction data and DFT comparison.

The crystal structure of dicesium hydrogen citrate, 2Cs+·C6H6O72-, has been solved using laboratory X-ray single-crystal diffraction data, refined using laboratory powder X-ray data, and optimized using density functional techniques. The Cs+ cation is nine-coordinate, with a bond-valence sum of 0.92 valence units. The CsO9 coordination polyhedra share edges and corners to form a three-dimensional framework. The citrate anion is located on a mirror plane. Its central hy-droxy/carboxyl-ate O-H⋯O hydrogen bond is short, and (unusually) inter-molecular. The centrosymmetric end-end carboxyl-ate hydrogen bond is exceptionally short (O⋯O = 2.416 Å) and strong. These hydrogen bonds contribute 16.5 and 21.7 kcal mol-1, respectively, to the crystal energy. The hydro-phobic methyl-ene groups occupy pockets in the framework.

Flexible ferroelectric organic crystals.

Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity-the properties that originate from their non-centrosymmetric crystal lattice-but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals.

Disodium hydrogen citrate sesquihydrate, Na2HC6H5O7(H2O)1.5.

The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2 (+)·C6H6O7 (2-)·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carb-oxy-lic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O⋯O distances of 2.46 Å.

Capturing neon - the first experimental structure of neon trapped within a metal-organic environment.

Despite being the fifth most abundant element in the atmosphere, neon has never been observed in an organic or metal-organic environment. This study shows the adsorption of this highly unreactive element within such an environment and reveals the first crystallographic observation of an interaction between neon and a transition metal.

Quantum Mechanical and Experimental Validation that Cyclobis(paraquat-p-phenylene) Forms a 1:1 Inclusion Complex with Tetrathiafulvalene.

The promiscuous encapsulation of π-electron-rich guests by the π-electron-deficient host, cyclobis(paraquat-p-phenylene) (CBPQT(4+)), involves the formation of 1:1 inclusion complexes. One of the most intensely investigated charge-transfer (CT) bands, assumed to result from inclusion of a guest molecule inside the cavity of CBPQT(4+), is an emerald-green band associated with the complexation of tetrathiafulvalene (TTF) and its derivatives. This interpretation was called into question recently in this journal based on theoretical gas-phase calculations that reinterpreted this CT band in terms of an intermolecular side-on interaction of TTF with one of the bipyridinium (BIPY(2+)) units of CBPQT(4+), rather than the encapsulation of TTF inside the cavity of CBPQT(4+). We carried out DFT calculations, including solvation, that reveal conclusively that the CT band emerging upon mixing TTF with CBPQT(4+) arises from the formation of a 1:1 inclusion complex. In support of this conclusion, we have performed additional experiments on a [2]rotaxane in which a TTF unit, located in the middle of its short dumbbell, is prevented sterically from interacting with either one of the two BIPY(2+) units of a CBPQT(4+) ring residing on a separate [2]rotaxane in a side-on fashion. This [2]rotaxane has similar UV/Vis and (1)H NMR spectroscopic properties with those of 1:1 inclusion complexes of TTF and its derivatives with CBPQT(4+). The [2]rotaxane exists as an equimolar mixture of cis- and trans-isomers associated with the disubstituted TTF unit in its dumbbell component. Solid-state structures were obtained for both isomers, validating the conclusion that the TTF unit, which gives rise to the CT band, resides inside CBPQT(4+).

A Hafnium-Based Metal-Organic Framework as a Nature-Inspired Tandem Reaction Catalyst.

Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new metal-organic framework (MOF) with porphyrinic struts and Hf6 nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when an Fe-decorated Hf6 node and the Fe-porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis.

Ultraporous, Water Stable, and Breathing Zirconium-Based Metal-Organic Frameworks with ftw Topology.

"Breathing" metal-organic frameworks (MOFs) are an emerging class of soft porous crystals (SPCs) with potential for high working capacity for gas storage applications. However, most breathing MOFs have low stability and/or low surface area. Here we report a water-stable, high surface area, breathing MOF of ftw topology, NU-1105. While Zr6-oxo clusters as nodes introduce water stability in NU-1105, its high surface area and breathing character stem from its pyrene-based tetracarboxylate (Py-FP) linkers, in which the fluorene units (F) in the FP "arms" play a key role in promoting breathing behavior. During gas sorption studies, the "closed pore" (cp) ↔ "open pore" (op) transition of NU-1105 occurs at a propane pressure of ∼3 bar. At 1 bar, NU-1105 is in its cp form and adsorbs less propane than it would in its op form, highlighting improved working capacity. In situ powder X-ray diffraction during propane sorption was used to track the cp ↔ op transition, and molecular modeling was used to elucidate the structure of the op and cp forms of NU-1105. According to TD-DFT calculations, the proposed conformations of the Py-FP linkers in the op and cp forms are consistent with the measured excitation and emission spectra of the op and cp forms of NU-1105. Similar structural transitions are also observed in the porphyrinic MOF NU-1104 depending on the identity of the porphyrin core; we observed breathing behavior if the constituent Por-PTP linker is nonmetalated.

Selective Solvent-Assisted Linker Exchange (SALE) in a Series of Zeolitic Imidazolate Frameworks.

Solvent-assisted linker exchange (SALE) has recently emerged as an attractive strategy for the synthesis of metal-organic frameworks (MOFs) that are unobtainable via traditional synthetic pathways. Herein we present the first example of selective SALE in which only the benzimiadazolate-containing linkers in a series of mixed-linker zeolitic imidazolate frameworks (ZIF-69, -78, and -76) are replaced. The resultant materials (SALEM-10, SALEM-10b, and SALEM-11, respectively) are isostructural to the parent framework and in each case contain trifluoromethyl moieties. We therefore evaluated each of these materials for their hydrophobicity in condensed and gas phases. We expect that selective SALE will significantly facilitate the design of improved, and potentially complex, MOF materials with new and unusual properties.