The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides

We have investigated using DFT methods the reaction mechanism of the Radzisewski reaction to obtain an amide via the reaction of ACN and H2O2 under alkaline conditions. The direct reaction between ACN and H2O2 showed a quite high activation energy (about 45 kcal mol-1) rendering this path unreliable. Instead, a fast reaction between ACN and HOO- forming the deprotonated species (PAIA-) of the peroxyacetimidic acid (PAIA) was observed. From this, PAIA- was guessed to form PAIA through a fast reaction of hydrolysis. Moreover, a second way of formation of PAIA, through an OH- catalyzed path, made the rate determining step (RDS) in very good agreement with experimental data, hence neglecting the contribution of the kinetically favored hydrolysis of PAIA-. This discrepancy was reconciled by considering that the final amide was obtained through a regioselective path forming the PAIA and the further reaction involving the decomposition of PAIA and PAIA-. Indeed, the PAIA obtained from the hydrolysis reaction showed a configuration which did not match the configurational behavior required. Conversely, the PAIA formed from the RDS path matched the required configuration needed to obtain the amide. Our findings also disentangled the experimenal debate on the assignment of the RDS.

(Ar-tpy)RuII(ACN)3: A Water-Soluble Catalyst for Aldehyde Amidation, Olefin Oxo-Scissoring, and Alkyne Oxygenation

The synthetic chemists always look for developing new catalysts, sustainable catalysis, and their applications in various organic transformations. Herein, we report a new class of water-soluble complexes, (Ar-tpy)Ru^II(ACN)₃, utilizing designed terpyridines possessing electron-donating and -withdrawing aromatic residues for tuning the catalytic activity of the Ru(II) complex. These complexes displayed excellent catalytic activity for several oxidative organic transformations including late-stage C-H functionalization of aldehydes with NH₂OR to valuable primary amides in nonconventional aqueous media with excellent yield. Its diverse catalytic power was established for direct oxo-scissoring of a wide range of alkenes to furnish aldehydes and/or ketones in high yield using a low catalyst loading in the water. Its smart catalytic activity under mild conditions was validated for dioxygenation of alkynes to highly demanding labile synthons, 1,2-diketones, and/or acids. This general and sustainable catalysis was successfully employed on sugar-based substrates to obtain the chiral amides, aldehydes, and labile 1,2-diketones. The catalyst is recovered and reused with a moderate turnover. The proposed mechanistic pathway is supported by isolation of the intermediates and their characterization. This multifaceted sustainable catalysis is a unique tool, especially for late-stage functionalization, to furnish the targeted compounds through frequently used amidation and oxygenation processes in the academia and industry.

Discovery of 3-Ethyl-4-(3-isopropyl-4-(4-(1-methyl-1 H-pyrazol-4-yl)-1 H-imidazol-1-yl)-1 H-pyrazolo[3,4- b]pyridin-1-yl)benzamide (TAS-116) as a Potent, Selective, and Orally Available HSP90 Inhibitor

The molecular chaperone heat shock protein 90 (HSP90) is a promising target for cancer therapy, as it assists in the stabilization of cancer-related proteins, promoting cancer cell growth, and survival. A novel series of HSP90 inhibitors were discovered by structure-activity relationship (SAR)-based optimization of an initial hit compound 11a having a 4-(4-(quinolin-3-yl)-1 H-indol-1-yl)benzamide structure. The pyrazolo[3,4- b]pyridine derivative, 16e (TAS-116), is a selective inhibitor of HSP90α and HSP90β among the HSP90 family proteins and exhibits oral availability in mice. The X-ray cocrystal structure of the 16e analogue 16d demonstrated a unique binding mode at the N-terminal ATP binding site. Oral administration of 16e demonstrated potent antitumor effects in an NCI-H1975 xenograft mouse model without significant body weight loss.

Resolving the Iron Phthalocyanine Redox Transitions for ORR Catalysis in Aqueous Media

Metal macrocycles are among the most important catalytic systems in electrocatalysis and biocatalysis owing to their rich redox chemistry. Precise understanding of the redox behavior of metal macrocycles in operando is essential for fundamental studies and practical applications of this catalytic system. Here we present electrochemical data for the representative iron phthalocyanine (FePc) in both aqueous and nonaqueous media coupled with in situ Raman and X-ray absorption analyses to challenge the traditional notion of the redox transition of FePc at the low potential end in aqueous media by showing that it arises from the redox transition of the ring. Our data unequivocally demonstrate that the electron is shuttled to the Pc ring via the Fe(II)/Fe(I) redox center. The Fe(II)/Fe(I) redox transition of FePc in aqueous media is indiscernible by normal spectroscopic methods owing to the lack of a suitable axial ligand to stabilize the Fe(I) state.

A novel prodrug strategy for beta-dicarbonyl carbon acids: syntheses and evaluation of the physicochemical characteristics of C-phosphoryloxymethyl (POM) and phosphoryloxymethyloxymethyl (POMOM) prodrug derivatives

The C-phosphoryloxymethyl (POM) and phosphoryloxymethyloxymethyl (POMOM) prodrugs resulting from derivatization at the reactive alpha-carbon of beta-dicarbonyl carbon acid drugs represent a unique approach for improving their chemical stability and aqueous solubility. This work evaluates the physicochemical and in vitro enzymatic bioconversion lability of selected prodrugs of phenylbutazone and phenindione. The POM and POMOM prodrug derivatives of phenylbutazone are highly water soluble (>or=250 mg/mL), chemically stable with projected shelf-lives of 4.5 years (pH 3.5, 25 degrees C) and 1.1 years (pH 6.0, 25 degrees C), respectively. Interestingly, both prodrug derivatives do not display a pH-dependency typical of many phosphate monoesters, although the similarities of their apparent thermodynamic activation parameters indicate a hydrolysis mechanism similar to other phosphates. These prodrugs undergo alkaline phosphatases catalyzed bioconversion to their respective carbon acids with an expected faster rate exhibited by the POMOM derivatives. Additionally, in marked contrast to the oxidative instability of phenindione, its POM prodrug is stable. The results from these studies reaffirm the rationale of transiently "masking" the reactive alpha-carbon/proton bond by covalently incorporating a POM or POMOM promoiety. This prodrug strategy presents a twofold advantage, enhancement of aqueous solubility and prevention of oxidative instability, two intrinsic formulation limitations found for beta-dicarbonyl carbon acid drugs.

Discovery of novel 2-aminobenzamide inhibitors of heat shock protein 90 as potent, selective and orally active antitumor agents

A novel class of heat shock protein 90 (Hsp90) inhibitors was developed from an unbiased screen to identify protein targets for a diverse compound library. These indol-4-one and indazol-4-one derived 2-aminobenzamides showed strong binding affinity to Hsp90, and optimized analogues exhibited nanomolar antiproliferative activity across multiple cancer cell lines. Heat shock protein 70 (Hsp70) induction and specific client protein degradation in cells on treatment with the inhibitors supported Hsp90 inhibition as the mechanism of action. Computational chemistry and X-ray crystallographic analysis of selected member compounds clearly defined the protein-inhibitor interaction and assisted the design of analogues. 4-[6,6-Dimethyl-4-oxo-3-(trifluoromethyl)-4,5,6,7-tetrahydro-1H-indazol-1-yl]-2-[(trans-4-hydroxycyclohexyl)amino]benzamide (SNX-2112, 9) was identified as highly selective and potent (IC(50) Her2 = 11 nM, HT-29 = 3 nM); its prodrug amino-acetic acid 4-[2-carbamoyl-5-(6,6-dimethyl-4-oxo-3-trifluoromethyl-4,5,6,7-tetrahydro-indazol-1-yl)-phenylamino]-cyclohexyl ester methanesulfonate (SNX-5422, 10) was orally bioavailable and efficacious in a broad range of xenograft tumor models (e.g. 67% growth delay in a HT-29 model) and is now in multiple phase I clinical trials.

Effects of superoxide anion generated from aromatic radical anions produced in nucleophilic aromatic photosubstitution reactions

Superoxide anion is generated from aromatic radical anions produced in nucleophilic aromatic photosubstitutions when the reactions are carried out in non-deoxygenated solutions of polar aprotic solvents. Superoxide anion thus generated displaces cyanide anion from acetonitrile and benzyl cyanide, ethoxide anion from ethyl acetate, and methanesulfenate anion from dimethyl sulfoxide. Hence, non-deoxygenated polar aprotic solvents should be avoided in nucleophilic aromatic photosubstitution reactions.Key words: superoxide, fluoride, nucleophilic aromatic photosubstitution.

The interactions of superoxide ion(O2-.) with metallo-porphyrins [(C1(8)TPP)M, M = Fe,Mn,Co Zn]; models for biological systems and superoxide dismutases

In dimethylformamide superoxide ion forms a 1:1 adduct with tetrakis (2,6-dichlorophenyl) porphinato-iron, (C1(8)TPP)FeOO-, as well as with its manganese analogue, (C1(8)TPP)MnOO-. On the basis of their electrochemical, spectroscopic, and magnetic properties these adducts have a metal-oxygen covalent bond (PorM-OO-), oxygen-centered redox chemistry, and reactivities that are similar to the hydroperoxide ion (HOO-). Addition of -OH to a solution of PorFe and O2 results in the formation of PorFe(OH)(OO-), which can be electrochemically oxidized to PorFeOH plus O2 (-0.2 V vs SCE). Addition of protons to the PorM-OO- adducts promotes their rapid decomposition to PorM, HOOH, and O2. This chemistry provides insight to the reactions of biological superoxide and superoxide dismutases.