Subsequent Elimination Reaction Research Articles

In Situ Fluorescence Imaging Reveals Contribution of Cerebral Hydroxyl Radicals in Hyperhomocysteinemia-Induced Alzheimer-like Dementia.

Elevated plasma level of homocysteine, also termed as hyperhomocysteinemia, is acknowledged as a significant and independent risk factor of Alzheimer's disease. However, the mechanistic insight has not been thoroughly elucidated yet. In this work, 3,5-dihydroxybenzyloxy was explored as the unique reaction trigger and integrated into the naphthalimide fluorophore via a carbamate linker to afford a new probe for •OH imaging. •OH treatment induced aromatic hydroxylation and subsequent elimination reaction to release the caged fluorophore, accompanied with a highly specific and sensitive turn-on fluorescence response. Cell imaging results revealed that excess homocysteine triggered overwhelming •OH production, which was mediated by N-methyl-d-aspartate receptor and NADPH oxidase, and the resultant •OH stress further initiated neuronal ferroptosis, also confirmed by western blot analyses. Additionally, hyperhomocysteinemic mouse models were established, and Alzheimer-like dementia of the mice was observed from behavioral tests. Most importantly, with this probe, cerebral •OH fluctuation was in situ visualized in live mice, which positively correlated with the severity of Alzheimer-like dementia induced by hyperhomocysteinemia. These results reveal that cerebral •OH stress may be the critical nexus linking hyperhomocysteinemia and Alzheimer's disease. This work provides a robust fluorescence probe for in situ visualizing the cerebral •OH fluctuations and illuminating critical insights into •OH contributions in brain disorders.

Synthesis of Amino-Acid-Based Nitroalkenes

Fatty-acid-based nitroalkenes have recently received great attention because of their bioactivities. On the contrary, peptide- or amino-acid-based nitroalkenes have been scarcely explored so far, although they may exhibit interesting biological properties, for example, as enzyme inhibitors. In this work, we study protocols for the efficient synthesis of nitroalkenes based on natural amino acids. A variety of N-protected amino alcohols and Weinreb amides, derived from α-amino acids, were converted to the corresponding N-protected amino aldehydes, and, through a Henry reaction with nitroalkanes, produced the corresponding nitro alcohols. The subsequent elimination reaction led to the (E)-isomer of amino-acid-based nitroalkenes in moderate to high yields.

Serendipitous One-Step Synthesis of Cyclopentene Derivatives from 5'-Deoxy-5'-heteroarylsulfonylnucleosides as Nucleoside-Derived Julia-Kocienski Reagents.

A serendipitous one-step transformation of 5'-deoxy-5'-heteroarylsulfonylnucleosides into cyclopentene derivatives is reported. This unique transformation likely proceeds via a domino reaction initiated by α-deprotonation of the heteroaryl sulfone and subsequent elimination reaction to generate a nucleobase and an α,β-unsaturated sulfone that contains a formyl group. The Michael addition of the nucleobase to the α,β-unsaturated sulfone and the subsequent intramolecular Julia-Kocienski reaction eventually generate the cyclopentene ring. Heteroarylthio and acylthio groups can be incorporated into the cyclopentene core in place of the nucleobase by conducting this reaction in the presence of a heteroarylthiol and a thiocarboxylic acid, respectively. cis,cis-Trisubstituted cyclopentene derivatives are obtained as a single stereoisomer from ribonucleoside-derived Julia-Kocienski sulfones.

Group 13-derived radicals from α-diimines via hydro- and carboalumination reactions.

The mechanochemical synthesis of tertiary and secondary alanes AlR3 (R = Np 1 or Mes 2; HAlR2 R = Np 3 or Mes 4) is described. These species are reacted with several α-diimines to give a series of aluminium-derived radicals of the form [(diimine)AlR2]˙ (6-11). EPR and several crystallographic studies are reported. These species are thought to form via hydro- or carboalumination and subsequent elimination reactions. This view is supported by the structural data for minor products C12H7(NHDipp)(NDipp)AliBu25 and C13H8(C(iBu)[double bond, length as m-dash]N(m-Xy)(NH(m-Xy)))AliBu212. In addition, the characterization of (C6F5)2B(OC(C6F5)OC12H8) indicates that such a carboboration pathway also provides access to related boron-derived radicals.

Synthetic Approach to Benzocyclobutenones Using Visible Light and a Phosphonate Auxiliary.

Reported herein is a two-step procedure to synthesize benzocyclobutenones from (o-alkylbenzoyl)phosphonates. It consists of a visible-light-driven cyclization reaction forming phosphonate-substituted benzocyclobutenols and subsequent elimination reaction of the H-phosphonate, which assumes a key role as the recyclable auxiliary. A wide variety of functionalized benzocyclobutenones, which include those difficult to synthesize by conventional methods, are efficiently synthesized.

An ESIPT-based mitochondria-targeted ratiometric and NIR-emitting fluorescent probe for hydrogen peroxide and its bioimaging in living cells

A mitochondria-targetable ratiometric fluorescent probe, HBTPB, has been developed for the detection of H2O2 with a near infrared (NIR) emission and a large Stokes shift (357 nm). Probe HBTPB displays high selectivity toward H2O2 over other reactive oxygen/nitrogen species (ROS/RNS), biological thiols and anions. The detection limit of this probe is as low as 5.9 × 10−7 M. The sensing process confirmed by NMR and mass spectral analysis shows that the addition of H2O2 to the solution of HBTPB triggers an oxidative hydrolysis and a subsequent elimination reaction undergoes to release an ESIPT (excited-state intramolecular proton transfer) featured fluorescent dye. Probe HBTPB is cell permeable and has been applied to sense exogenous and endogenous H2O2 in living A549 cells.

Cu(OAc)2-Mediated Reaction of [60]Fullerene with Aldehydes and Primary Amines for the Synthesis of Fulleropyrrolines.

The facile one-step reaction of [60]fullerene with aldehydes and primary amines in the presence of cheap and easily available Cu(OAc)2·H2O afforded a series of new types of fulleropyrrolines with trisubstituted C═C bonds in good to excellent yields, which would be difficult to prepare by known methods. The formed fulleropyrroline under the assistance of Pd(OAc)2 and CuCl2·2H2O could be further converted to 1-fulleropyrrolidine by the chlorohydroxylation reaction of C═C bond. Subsequent elimination reaction of 1-fulleropyrrolidine with the aid of TsOH·H2O generated the scarce 1-fulleropyrroline derivative.

Highly regioselective synthesis of 4-tosylthiomorpholine via intramolecular cyclization of N-tethered thioalkenols.

A one-pot, metal-free procedure has been developed for the synthesis of 4-tosylthiomorpholine from N-tethered thioalkenols via bromination, cyclization and subsequent elimination reaction in good yields. The reaction is found to be highly regioselective.

ChemInform Abstract: Ce(OTf)3‐Catalyzed [3 + 2] Cycloaddition of Azides with Nitroolefins: Regioselective Synthesis of 1,5‐Disubstituted 1,2,3‐Triazoles.

AbstractBoth benzyl and phenyl azides react with a broad range of aryl nitroolefins selectively to the title compounds through cycloaddition and subsequent elimination reaction.

Ce(OTf)₃-catalyzed [3 + 2] cycloaddition of azides with nitroolefins: regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles.

The first example of rare earth metal-catalyzed [3 + 2] cycloaddition of organic azides with nitroolefins and subsequent elimination reaction is described. In the presence of a catalytic amount of Ce(OTf)3, both benzyl and phenyl azides react with a broad range of aryl nitroolefins containing a range of functionalities selectively producing 1,5-disubstituted 1,2,3-triazoles in good to excellent yields.

Syntheses of p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene by one-pot benzannulation of Diels–Alder reactions of trans-1,2-dichloroethene and dienes

A series of substituted p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene were successfully synthesized by one-pot benzannulation of Diels–Alder reaction with 1,2-dichloroethene as an acetylene equivalent dienophile. Two chlorine atoms could be good leaving groups to easily undergo subsequent elimination reactions of Diels–Alder products at a high temperature.

Solid-Phase Organic Synthesis of Aryl Vinyl Ethers Using Sulfone-Linking Strategy

A novel facile solid-phase organic synthesis of aryl vinyl ethers by reaction of polystyrene-supported 2-phenylsulfonylethanol with phenols under Mitsunobu conditions and subsequent elimination reaction with DBU has been developed. The advantages of this method include straightforward operation, good yield and high purity of the products. Alternatively, a typical example of Suzuki coupling reaction on-resin was further applied to prepare 4-phenylphenyl vinyl ether for extending this method.

Single Step Conversion of Chiral Carnitine and Derivatives into (S)- and (R)-β-Substituted-γ-Butyrolactones

This paper describes an efficient single step transformation of chiral carnitine and carnitine derivatives into stereoisomerically pure (S)- and (R)-β-substituted-γ-butyrolactones, obtained by intramolecular nucleophilic displacement. (S)- Or (R)-carnitine and (R)-aminocarnitine inner salts give β-hydroxy-γ-butyrolactone and β-amino-γ-butyrolactone respectively (82% and 77%) with the same configuration as the starting material. (R)-Acetylaminocarnitine inner salt gives (R)-β-acetylamino-γ-butyrolactone (90%), while (R)-acetylcarnitine gives 2(5H)-furanone under the same reaction conditions (77%, via cyclization and subsequent elimination reaction). (R)-N-Benzyloxycarnitineamide gives a mixture of pyrrolidinone (11%) and furanoyl imidate (50%) derivatives. The direct transformation of wast (S)-carnitine into the valuable (S)-β-hydroxy-γ-butyrolactone or (after acetylation) into the precious 2(5H)-furanone is of particular interest.

Synthesis of 1-Amino-2-naphthalenecarboxylic Acid Derivatives via the Intramolecular Cyclization of 4-(2-Cyanophenyl)-2-butenoic Acid Derivatives and Its Application to the One-Pot Preparation of Benzo[h]quinazoline-2,4(1H,3H)-diones

Abstract The reaction of 2-(lithiomethyl)benzonitrile with 2-phenylthio-2-alkenoic acid derivatives in diglyme at −78 °C, followed by oxidation with sodium metaperiodate in aqueous MeOH at room temperature and the subsequent elimination reaction in refluxing toluene, gave 4-(2-cyanophenyl)-2-butenoic acid derivatives in moderate-to-fair overall yields. Intramolecular cyclization of these products using NaH in DMF at 0 °C gave 1-amino-2-naphthalenecarboxylic acid derivatives almost quantitatively. Successive treatments with an isocyanate without isolation of the aminonaphthalenecarboxylates under reflux afforded benzo[h]quinazoline-2,4(1H,3H)-diones in moderate-to-good yields.

Use of Differential Scanning Calorimetry and Thermogravimetric Analysis To Characterize the Thermal Degradation of Crystalline Sucrose and Dried Sucrose−Salt Residues

Thermal degradation of pure sucrose in concentrated aqueous solution (100 °C, ∼65 °Brix) in the presence of KCl, LiCl, NaI, and Na2B4O7 was investigated. Polarimetry was used to quantify sucrose degradation, and pseudo-first-order kinetic constants of initial degradation rates were calculated. All salts significantly increased sucrose degradation; colored degradation products were only formed in the presence of Na2B4O7. Thermal degradation characteristics of crystalline sucrose and dried, crystalline residues from sucrose−salt model solutions heated at 100 °C for 0 and 3 h were further investigated by differential scanning calorimetry (DSC), thermogravimetric (TG), and differential thermogravimetric (DTG) analyses. Rate of heating was 15 °C/min from 50 to 500 °C. DSC and TG studies confirmed the catalytic nature of salts on the thermal degradation of sucrose. Salts affected thermal degradation in various ways. The initial condensation degradation reactions were more rapid than expected, and subsequent elimination reactions were slower. The thermal analysis results indicate that complexation between the salt and sucrose is occurring, and further study at the molecular level is required. Keywords: Sucrose thermal degradation; DSC; TG, DTG; salts; crystalline sucrose; amorphous sucrose

ChemInform Abstract: Kinetics and Mechanism of the Cyclization of Some 2′‐Hydroxychalcone Epoxides and Subsequent Elimination Reactions of Aurone Hydrates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Kinetics and mechanism of the cyclisation of some 2′-hydroxy-chalcone epoxides and subsequent elimination reactions of aurone hydrates

Abstract Analysis of the pH-rate profile for the cyclisation of the monoanion of 2′-hydroxychalcone epoxide which gives 3-hydroxyflavanone and of some 6′-alkoxy-substituted analogues which give mostly hydrate, gives rate coefficients which quantify the preference for α over β cyclisation when 6′-substituents are present. These are considered in terms of stereoelectronic factors which may be responsible for the preference. Also reported are rate coefficients for the subsequent reaction of aurone hydrates in which aurones and coumaranones are formed.

ChemInform Abstract: Some Valenes of Benzoanellated Five‐Membered Heteroarenes ‐ Syntheses and NMR Spectra.

Abstract1,3‐Dipolar cycloaddition reactions of the benzvalenylsulfone (I) with compounds such as (II) or (VI) and subsequent elimination reaction of the products (III) or (VIII) give rise to valenes such as (V) or (IX).

ChemInform Abstract: Total Synthesis of 12α‐ and 12β‐Carboxylated Estrogens via the Thermal Elimination of β‐Ketosulfoxide.

AbstractAlkylation of the keto sulfoxide (I) with methyl bromoacetate (II) and subsequent elimination reaction produce the enone ester (IV) which is cyclized to form a mixture of the estrapentaenones (VII) after addition of 2‐methylcyclopentane‐1,3‐dione (V).

ChemInform Abstract: Interaction Between Non‐Conjugated Chromophores. Part.25. Diels‐Alder Regioselectivity Controlled by Remote Substituents.

Abstract1. The synthesis of the methylidene compounds (I) and (II) is reported: The ester (IVa) [obtained from the anhydride (IIIa)] is transformed to the mesylate (IVc) via (IVb); subsequent elimination reaction furnishes (Ia) which is converted to (Ib) and (Ic) by standard reactions.