Studies on the Stereoselective Synthesis of Sacubitril via a Chiral Amine Transfer Approach.

We present a comprehensive account of our efforts directed towards the synthesis of sacubitril, a neprilysin inhibitor used in combination with valsartan and marketed as Entresto™. Our initial approach to the formal synthesis of sacubitril employed a chiral pool strategy, utilizing (S)-pyroglutamic acid as a key building block and Cu(I)-mediated Csp2-Csp3 cross-coupling as a key transformation. Further investigations led to the development of chiral amine transfer (CAT) reagents-based stereoselective synthesis.

A Pair of Dinuclear Fe(II) Enantiomers: Syntheses and Structures of ΛΔ/ΔΛ-Bis(Dihydridoborate) Complexes.

In our effort to establish a direct synthetic approach for bis(dihydridoborate) complexes of first-row transition metals, we have investigated the reactivity of [Cp*Fe(dppe)Cl] (dppe =1,2-bis(diphenylphosphino)ethane) with Na[BHL] (L =2-mercaptopyridine (mp) and 2-mercaptobenzothiazole (mbz)) that led to the formation of iron(II) dihydridoborate complexes, [Cp*Fe{κ-S,H,H-(HBH(L))}] 1 a-b (L=mp (1 a) and L=mbz (1 b)). Further, in an attempt to isolate the bis(dihydridoborate) complex of iron by the insertion of borane into the κ-N,S-chelated iron complex, [(dppe)Fe{κ-N,S-(mp)}] (2), we have isolated and structurally characterized a rare example of dimeric iron bis(dihydridoborate) complex, [Fe{κ-S,H,H-(HBH(mp))}], ΛΔ/ΔΛ-3 as pair of enantiomers. Interestingly, these enantiomers ΛΔ/ΔΛ-3 have two trans-[Fe{κ-S,H,H-(HBH(mp))}] moieties bridged through sulfur atoms of 2-mercaptopyridinyl ligands, where the iron centres are hepta-coordinated.

Unprecedented C-F bond cleavage in perfluoronaphthalene during cobaltocene reduction.

The C-F bond activation of perfluoronaphthalene by 5-SIDipp led to the formation of dicationic salts with two fluorides (3·2HF2 ) or heptafluorodiborate (3·2B2F7) as counter-anions. The anion exchange reaction of 3·2B2F7 with NBuPF afforded a highly luminescent 3·2PF6. The addition of cobaltocene in the reaction mixture of 5-SIDipp and perfluoronaphthalene led to a distinct Co(I) species.

Uncovering diverse reactivity of NHCs with diazoalkane: C-H activation, C[double bond, length as m-dash]C bond formation, and access to N-heterocyclic methylenehydrazine.

N-heterocyclic carbenes (NHCs) have attracted significant attention due to their strong σ-donating capabilities, as well as their transition-metal-like reactivity towards small molecules. However, their interaction with diazoalkanes remains understudied. In this manuscript, we explore the reactivity of a series of stable carbenes, encompassing a wide range of electronic properties, with MeSiCHN.

Rational Monomer Design for the Synthesis of Conjugated Polymers by Direct Heteroarylation Polymerization.

This study focuses on the design concepts that contribute to the C-H activation in bithiophene-flanked monomers incorporating naphthalene diimide (NDI), perylene diimide (PDI), and fluorene (FLU) and their polymerization by direct heteroarylation. Density functional theory (DFT) calculations reveal distinct energy requirements for C-H bond abstraction, which is dictated by the electron-withdrawing strength of the central aromatic core flanked by bithiophene. These provide insights into the reactivity of each monomer for C-H bond activation.

Germylene Mediated Reductive C-C and C-N Coupling of an Isocyanide and its Device Application.

We have demonstrated a unique reductive coupling of 4-iodophenyl isocyanide, facilitated by a perimidine-based N-heterocyclic germylene (NHGe), which yields a bis-spirogerma compound featuring simultaneous C-C and C-N bond formation. This reaction, which leads to the oxidation of germanium from +2 to +4, represents a significant departure from previously documented isocyanide-germylene interactions. The product exhibits extensive conjugation across its bicyclic CGeN framework, conferring distinct photophysical properties, including prominent orange luminescence in both solution and solid states.

Unravelling the prebiotic origins of the simplest α-ketoacids in cometary ices: a computational investigation.

We have employed the nanoreactor (AINR) and DFT calculations to explore how the soft impact of comets entering early earth's dense atmosphere could induce chemical reactions in trapped interstellar ice components, leading to the origin of glyoxylic and pyruvic acids the simplest α-ketoacids essential for prebiotic metabolic cycles.

Depolymerization of Waste Polycarbonates to Value-Added Products.

Additive free aminolysis method developed for the depolymerization/upcycling of polycarbonates. We report here chemical recycling of polycarbonate under ambient conditions to get its monomer bisphenol A, monoaminocarbamate and biscarbamates in 1 : 2 : 1 ratio respectively. By employing the secondary amine as the aminating reagent, facilitates the depolymerization to work under additive/catalyst free conditions.

Unveiling the Inverse Sandwich Complexes of XeO: A Computational Exploration.

Our study introduces the design of inverse sandwich (iSw) complexes incorporating a noble gas compound: xenon trioxide (XeO). Through comprehensive computational analyses, we have investigated the critical factors influencing their stability by employing a variety of state-of-the-art computational tools. We demonstrated that the coordination number of xenon in the iSw complex of XeO with 18-crown-6 is influenced by the presence of a rare, weakly stabilizing Xe···Xe interaction between the XeO molecules.

Taming XeO with Aza-Crowns: Computational Studies into σ-Hole Mediated Host-Guest Interactions.

Various aza-crowns with different sizes and substituents have been explored computationally as potential hosts for stabilizing the explosive guest xenon trioxide (XeO) through σ-hole-mediated aerogen bonding interactions. Interestingly, aza-crowns demonstrate superior binding towards XeO compared to their oxygen and thio counterparts. However, unlike the latter cases, where the binding was found to be increasingly favorable with the increase in the size of the crowns, aza-crowns exhibit a variable size preference for XeO, peaking with aza-15-crown-5, and reducing thereafter with increase in crown size.

Brønsted Acid-Promoted Cyclodimerization of α,β-Unsaturated γ-Ketoesters: Construction of Fused Pyrano-ketal-lactones and γ-Ylidene-butenolides.

Unprecedented MsOH-promoted diastereoselective cascade dimerization and intramolecular lactonization of readily accessible α,β-unsaturated γ-ketoesters are presented. The results obtained in this work, control experiments, and density functional theory (DFT) calculations suggested that the initial enolization and to isomerization/equilibration of olefin (C=C) of substrate α,β-unsaturated γ-ketoesters give a -isomer preferentially over an -isomer. Subsequently, the -isomer undergoes intermolecular annulation with α,β-unsaturated γ-ketoesters via domino Michael addition/ketalization/lactonization steps to furnish fused tetracyclic pyrano-ketal-lactone.

Effect of Position of Donor Units and Alkyl Groups on Dye-Sensitized Solar Cell Device Performance: Indoline-Aniline Donor-Based Visible Light Active Unsymmetrical Squaraine Dyes.

Indoline (In) and aniline (An) donor-based visible light active unsymmetrical squaraine (SQ) dyes were synthesized for dye-sensitized solar cells (DSSCs), where the position of An and In units was changed with respect to the anchoring group (carboxylic acid) to have In-SQ-An-COH and An-SQ-In-COH sensitizers, . Linear or branched alkyl groups were functionalized with the N atom of either In or An units to control the aggregation of the dyes on TiO. exhibit an isomeric π-framework where the squaric acid unit is placed in the middle, where and dyes possess the anchoring group connected with the An donor, and , , and dyes having the anchoring group connected with the In donor.

Size Matters: Computational Insights into the Crowning of Noble Gas Trioxides.

In pursuit of enhancing the stability of the highly explosive and shock-sensitive compound XeO, we performed quantum chemical calculations to investigate its possible complexation with electron-rich crown ethers, including 9-crown-3, 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7, as well as their thio analogues. Furthermore, we expanded our study to other noble gas trioxides (NgO), namely, KrO and ArO. The basis set superposition error (BSSE) corrected interaction energies for these adducts range from -13.

Far-red active unsymmetrical squaraine dyes containing N-arylated indoline donors for dye sensitized solar cells.

Squaraine dyes possess sharp far-red active transition with high extinction coefficient and form aggregates on TiO surface. Aggregation of dyes on TiO has been considered as a detrimental factor for DSSC device performance, which can be controlled by appending alkyl groups to the dye structures. Hence by integrating alkylated (alkyl groups with both in-plane and out-of-plane) aryl group with indoline moiety to make it compatible with other electrolytes and for controlling the dye-aggregation, a series of squaraine acceptor-based dyes SQA4-6 have been designed and synthesized.

The Role of Aromatic Alcohol Additives on Asymmetric Organocatalysis Reactions: Insights from Theory.

The presence of an aromatic additive has been seen to enhance, often significantly, the enantioselectivity and yield in asymmetric organocatalysis. Considering their success across a dizzying range of organocatalysts and organic transformations, it would seem unlikely that a common principle exists for their functioning. However, the current investigations with DFT suggest a general principle: the phenolic additive sandwiches itself, through hydrogen bonding and π⋅⋅⋅π stacking, between the organocatalyst coordinated electrophile and nucleophile.

Exploring Unconventional σ-Hole Interactions: Computational Insights into the Interaction of XeO with Non-Aromatic Coordinating Solvents.

In order to control the explosiveness and shock sensitivity of XeO , we have investigated its plausible interaction with various non-aromatic coordinating solvents, serving as potential Lewis base donors, through density functional theory (DFT) calculations. Out of twenty six such solvents, the top ten were thus identified and then thoroughly examined by employing various computational tools such as the mapping of the electrostatic potential surface (MESP), Wiberg bond indices (WBIs), non-covalent interaction (NCI) plots, Bader's theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, and the energy decomposition analysis (EDA). The amphoteric nature of XeO was also explored by investigating the extent of back donation from the lone pair of Xe to the antibonding orbital of the donating atom/group of the solvent molecules.

Brønsted acid- and Ni(II)-catalyzed C-H oxidation/rearrangement of cyclotriveratrylenes (CTVs) to cyclic and acyclic quinones as potential anti-cancer agents.

This paper describes a simple and practical protocol for the direct synthesis of acyclic and cyclic quinone derivatives an acid-promoted nickel(II)-catalyzed inner rim C-H oxidation of cyclotriveratrylene (CTV) and its analogues. The cyclic quinone derivatives resulted from trimethoxy-cyclotriveratrylene (TCTV) through C-C bond formation intramolecular substitution followed by subsequent anionic rearrangement containing stereo-vicinal quaternary centers. The DFT calculations strongly support the experimental findings and reveal the role of Brønsted acids in the C-H bond activation of CTV.

Tridentate NacNac Tames T-Shaped Nickel(I) Radical.

The reaction of a nickel(II) chloride complex containing a tridentate β-diketiminato ligand with a picolyl group [2,6-iPr -C H NC(Me)CHC(Me)NH(CH py)]Ni(II)Cl (1)] with KSi(SiMe ) conveniently afforded a nickel(I) radical with a T-shaped geometry (2). The compound's metalloradical nature was confirmed through electron paramagnetic resonance (EPR) studies and its reaction with TEMPO, resulting in the formation of a highly unusual three-membered nickeloxaziridine complex (3). When reacted with disulfide and diselenide, the S-S and Se-Se bonds were cleaved, and a coupled product was formed through carbon atom of the pyridine-imine group.

Lanthanide Mimicking by Magnesium for Oxazolidinone Synthesis.

In the last decade, magnesium complexes have emerged as a viable alternative to transition-metal catalysts for the hydrofunctionalization of unsaturated bonds. However, their potential for advanced catalytic reactions has not been thoroughly investigated. To address this gap, we have developed a novel magnesium amide compound (3) using a PNP framework that is both bulky and flexible.

H-atom site exchange in an iridium -dihydrogen/hydride complex, -[Ir(H)(η-H)(POCOP)(DMAP)].

Treatment of -[Ir(H)(N)(POCOP)(DMAP)][BAr] (2) with H (1 bar) under ambient conditions (298 K) results in the formation of a -[Ir(H)(η-H)(POCOP)(DMAP)][BAr] (3) complex. Complex 3 exhibits H-atom site exchange between the bound H and the hydride ligands which are mutually to one another. A plausible mechanism of this exchange involves metal-ligand cooperativity as studied by computations.

Enhancing Diradical Character of Chichibabin's Hydrocarbon through Fluoride Substitution.

In this work, 5-SIDipp [SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] (1) derived Chichibabin's hydrocarbon with an octafluorobiphenylene spacer (3) has been reported. The addition of two equivalents of 5-SIDipp with decafluorobiphenyl in presence of BF gives the double C-F bond activated imidazolium salt with two tetrafluoroborate anions, 2. Further reduction of 2 gives the fluorine substituted 5-SIDipp based Chichibabin's hydrocarbon, 3.

On the competition between six-membered and five-membered NHC towards alane centered ring expansion.

The combination of 6-SIDipp·AlH (1) and 5-IDipp resulted in the ring expansion of 6-NHC, while the five-membered NHC remained unchanged, which was subsequently explained by DFT studies. Besides, the substitution chemistry of 1 was also studied with TMSOTf and I, which gave rise to the substitution of a hydride by triflate or iodide ligands.

Taming the parent oxoborane.

Despite recent advancements in the chemistry of multiply bound boron compounds, the laboratory isolation of the parent oxoborane moiety, HBO has long remained an unsolved and well-recognized challenge. The reaction of 6-SIDipp·BH [6-SIDipp = 1,3-di(2,6-diisopropylphenyl)tetrahydropyrimidine-2-ylidene] with GaCl afforded an unusual boron-gallium 3c-2e compound (1). The addition of water to 1 resulted in the release of H and the formation of a rare acid stabilized neutral parent oxoborane, LB(H)[double bond, length as m-dash]O (2).

The "Weak" C-H⋅⋅⋅S Interaction Drives Enantioselectivity in Cinchona Alkaloid Complex Catalyzed Thiocyanation.

The great success of asymmetric organocatalysis has made it one of the most important advancements made in chemistry in the past two decades. A significant achievement in this context is the asymmetric organocatalysis of the thiocyanation reaction. In the current study, computational studies with density functional theory have been done in order to understand an interesting experimental finding: the reversal of enantioselectivity from R to S when the electrophile is changed from β-keto ester to oxindole for the thiocyanation reaction with the cinchona alkaloid complex catalyst.

Controlled reduction of isocyanates to formamides using monomeric magnesium.

This work describes a transition metal-free methodology involving an efficient and controlled reduction of isocyanates to only formamide derivatives using pinacolborane (HBpin) as the hydrogenating agent and a bis(phosphino)carbazole ligand stabilized magnesium methyl complex (1) as the catalyst. A large number of substrates undergo selective hydroboration and give exclusively -boryl formamides.