Search

Two approaches involving intramolecular and intermolecular cyclization, respectively, have been developed for the direct and practical construction of a series of important benzo[ f ]pyrrolo[1,2- a ][1,4]azepines by using Brønsted acid catalysts. Upon catalysis by TsOH, the intramolecular dehydroxylation/ring closure of 3-hydroxy-2-[2-(1 H -pyrrol-1-yl)benzyl]isoindolin-1-ones provided various racemic benzo[ f ]pyrrolo[1,2- a ][1,4]azepines in high yields. Furthermore, enantioenriched benzo[ f ]pyrrolo[1,2- a ][1,4]azepines were also obtained by chiral phosphoric acid catalyzed intermolecular addition of [2-(1 H -pyrrol-1-yl)phenyl]methanamines to 2-formylbenzoates under mild conditions. [ABSTRACT FROM AUTHOR]

A novel process involving base-catalyzed intramolecular defluorination/O-arylation of readily available α-fluoro-β-one-sulfones was realized and provided a series of 3-fluoro-1,4-oxathiine 4,4-dioxide derivatives in good to excellent yields. Unlike traditional defluorination reactions with stoichiometric base as the deacid reagent, this process is triggered by a catalytic amount of base (TMG: tetramethylguanidine) and molecular sieves serve as both an adsorbent to remove HF acid and an activator to assist C–F bond cleavage. [ABSTRACT FROM AUTHOR]

Despite the widespread use of naphthamide atropisomers in biologically active compounds and asymmetric catalysis, few catalytic methods have succeeded in the enantioselective synthesis of these compounds. Herein, a chiral Brønsted acid (CBA) catalysis strategy was developed for readily scalable dynamic kinetic resolution of challenging ortho-formyl naphthamides with pyrrolylanilines. The chiral axis of the atropisomeric amide and a stereogenic center were simultaneously established for a new family of potential biologically active pyrrolopyrazine compounds with high enantio- and diastereoselectivities (up to >20 : 1 d.r. and 98 : 2 e.r.). Epimerization experiments of its derivatives reveal that the N-substitution of the nearby stereogenic center could affect the configurational stability of the axially chiral aromatic amides. These results might be useful for the construction of other kinds of novel axially chiral molecules with a low rotational barrier. [ABSTRACT FROM AUTHOR]

A Chiral Brønsted acid catalyzed asymmetric intramolecular ring‐closing alkylation of inert pyrroles with α, β‐unsaturated ketones has been developed. This approach gave a wide range of 4‐phenyl‐4,5‐dihydro‐6H‐benzo[f]pyrrolo[1,2‐a]azepin‐6‐ones in high yields with good enantioselectivities under mild reaction conditions. [ABSTRACT FROM AUTHOR]

A highly enantioselective regiodivergent addition of alkoxyallenes to pyrazolones was developed to afford multiply functionalized alkylated products bearing a quaternary carbon stereocenter in high yields with excellent stereoselectivities. One approach is enabled by palladium catalysis, thus leading to branched allylic pyrazol-5-ones under mild reaction conditions. The other is catalyzed by a chiral Brønsted acid to give linear products exclusively. Moreover, the usefulness of this new method was highlighted by converting the allylic products into other interesting multifunctionalized pyrazolone derivatives which would be of great potential for the exploitation of pharmaceutically important molecules. [ABSTRACT FROM AUTHOR]

A new approach has been established for Rh(iii)-catalyzed direct aza oxidative cyclization of non-prefunctionalized azobenzenes to provide 2-aryl-2H-benzotriazoles in good yields, in which AgNO3 instead of conventional azide reagents for the first time functions as the nitrogen source for the nitrogenation reaction. Preliminary mechanistic studies suggest that the Rh(iii)-catalyst could account for the nitration reaction, and subsequently cationic silver species might both play a vital role in the fission of the nitrogen–oxygen bonds in nitro groups and promote aza oxidative cyclization. [ABSTRACT FROM AUTHOR]

A practical, metal-free, and highlychemoselective approach wasdeveloped for the synthesis of ortho-CHO diaryl ethersby a three-component sequential coupling of arynes, N,N-dimethylformamide (DMF), and diaryliodoniumsalts. Diverse functional groups including halo, nitryl, and bulkysubstituents and heteroaromatics are well tolerated. Mechanistically,isotopic tracer experiments reveal that the diaryliodonium salt servesas an electrophile to trap the transient intermediates generated fromthe [2 + 2] cyclization of an aryne and DMF. [ABSTRACT FROM AUTHOR]

A Brønstedacid accelerated Pd-catalyzed asymmetric allylicalkylation of azlactones with simple allylic alcohols under mild reactionconditions has been realized, which provides a direct and readilyscalable approach for the synthesis of all-carbon quaternary allylicamino acid derivatives in excellent yields and good enantioselectivities. [ABSTRACT FROM AUTHOR]

A mass spectrometric study of protonated warfarin and its derivatives (compounds 1 to 5) has been performed. Losses of a substituted benzylideneacetone and a 4-hydroxycoumarin have been observed as a result of retro-Michael reaction. The added proton is initially localized between the two carbonyl oxygens through hydrogen bonding in the most thermodynamically favorable tautomer. Upon collisional activation, the added proton migrates to the C-3 of 4-hydroxycoumarin, which is called the dissociative protonation site, leading to the formation of the intermediate ion-neutral complex (INC). Within the INC, further proton transfer gives rise to a proton-bound complex. The cleavage of one hydrogen bond of the proton-bound complex produces the protonated 4-hydroxycoumarin, while the separation of the other hydrogen bond gives rise to the protonated benzylideneacetone. Theoretical calculations indicate that the 1, 5-proton transfer pathway is most thermodynamically favorable and support the existence of the INC. Both substituent effect and the kinetic method were utilized for explaining the relative abundances of protonated 4-hydroxycoumarin and protonated benzylideneacetone derivative. For monosubstituted warfarins, the electron-donating substituents favor the generation of protonated substituted benzylideneacetone, whereas the electron-withdrawing groups favor the formation of protonated 4-hydroxycoumarin. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The back cover of the journal "Angewandte Chemie International Edition" is presented.

Zwei katalytische Prozesse …… , nämlich Palladium ‐ Katalyse und Brønsted ‐ Säure ‐ Katalyse, liefern unterschiedliche Produkte bei der Addition von Alkoxyallenen an Pyrazolone. Wie G. Jiang et al. in ihrer Zuschrift auf S. 1097 zeigen, führt Pd ‐ Katalyse zu verzweigten allylischen Pyrazol ‐ 5 ‐ onen unter extrem milden Bedingungen, während eine chirale Brønsted ‐ Säure lineare Additionsprodukte ergibt. [ABSTRACT FROM AUTHOR]

The coupling between ortho-trimethylsilyl aryl triflates, N,N-dimethylformamide and diaryliodonium salts tolerates various functional groups. [ABSTRACT FROM AUTHOR]

Preliminary experiments towards an asymmetric allylation of (Ia) with (II) using chiral mono or diphosphine ligands furnish (IIIa) with up to 17% enantiomeric excess only. [ABSTRACT FROM AUTHOR]

The first efficient example of the direct allylic alkylation of azlactones with simple allylic alcohols using only Pd(PPh3)4 as catalyst under neutral conditions by substrate self-assisted activation strategy is reported. [ABSTRACT FROM AUTHOR]

The present study examined English use anxiety, motivation, self-efficacy, use of English, and their predictive effects on top university students' English achievements. Two hundred and twenty-three students of the Top-Notch Students of Basic Disciplines Training Program in a top Chinese university answered a battery of questionnaires, which consisted of the 8-item English Use Anxiety Questionnaire, the 5-item Motivational Self-Talk Questionnaire, the 3-item Self-Efficacy Questionnaire, the 19-item Language Learning Orientations Questionnaire, and a Background Information Questionnaire. Analyses of the data revealed the following major findings: (1) the participants had a low level of extrinsic motivation-introjected regulation, a low-to-medium level of English use anxiety, extrinsic motivation-external regulation, intrinsic motivation-knowledge, and a medium-to-high level of motivational self-talk, self-efficacy, extrinsic motivation-identified regulation, intrinsic motivation-accomplishment, and intrinsic motivation-stimulation, (2) use of English anxiety (UAE) and language learning orientation were generally significantly negatively correlated with each other, and significantly correlated with other measured variables, (3) UAE and intrinsic motivation-knowledge significantly predicted the participants English achievements, measured both by standardized test scores and self-rated overall English proficiency, and (4) use of English and self-efficacy mediated the effects of English use anxiety and language learning orientations on the participants' English achievements. These findings further pinpoint the importance of anxiety and motivation in second/foreign language learning., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wu, Yang, Liu and Liu.)

A family of axially chiral quinazolinone-based heterobiaryls were constructed with high levels of enantiocontrol (up to 94% ee). Convergently, three different synthetic methods have been realized to prepare these valuable compounds including central-to-axial chirality transfer, dynamic kinetic resolution, and phase-transfer catalysis. Importantly, novel P,N-ligands with a π-π stacking can be derived from heterobiaryls by chirality exchange strategy or synthesized directly from complementary phase-transfer catalysis by using the inexpensive chiral quaternary ammonium salt.

A novel intramolecular Smiles rearrangement of α-fluoro-β-keto-pyrimidylsulfones (usually used as a carbon nucleophile) was developed, providing a versatile avenue for synthesis of tri/tetra-substituted monofluorinated pyrimidyl enol ethers. Among these, diverse ( Z )-monofluorovinylsulfones and sulfinates were efficiently assembled by adding extra electrophile and fine-tuning reaction conditions. The process is triggered by a keto-enol tautomerism from enol oxyanion to pyrimidine 2-carbon, completely different from the classical carbon nucleophilic addition reaction approach.

Central-to-axial chirality transfer via C-N single bond oxidation was first achieved as a versatile and conceptually distinct strategy to prepare a new family of axially chiral heteroaromatic biaryl backbones and P,N-ligands (named as Quinoxalinaps) in gram scale. Two atropisomers of Quinoxalinaps (ee >99%) were readily accessed from the same precursor enantiomer by a simple dehydrogenative oxidation with MnO 2 and t -BuOOH under mild conditions. Phosphine could be introduced into the ligands before or after the chirality control process. Moreover, these Quinoxalinap P,N-ligands performed well for both asymmetric reactions of the CuBr-catalyzed alkyne conjugate addition with up to -94% ee and AgOAc-catalyzed glycinate imine [3 + 2] annulation with 90% ee, respectively.

A chiral Brønsted acid catalyzed highly enantio- and diastereoselective cascade cyclization has been developed to streamline the synthesis of valuable multifunctionalized enantioenriched cyclopenta[ f]pyrrolo[1,2- d][1,4]diazepinones bearing three contiguous stereocenters in high yields with excellent control of stereochemistry from a wide range of both readily available 2-furylcarbinols and (1 H-pyrrol-1-yl)anilines, which represents the first asymmetric intramolecular conjugate addition of α,β-unsaturated cycloketones with inert N-substituted pyrroles as well as the first enantioselective aza-piancatelli rearrangement/Friedel-Crafts alkylation cascade reaction.

A practical and readily scalable reaction sequence was developed for the straightforward synthesis of a new family of larger π-conjugated naphthopyrans by a Brønsted acid-catalyzed aromatic annulation of alkoxyallenes with inert naphthols. The cascade pathway involves allylation/cyclization/debenzyloxylation/isomerization/dehydration. The new class of solid state diphenylmethylene substituted naphthopyrans are fluorescent emissive and proved to have aggregation-induced emission (AIE) behavior.

A practical and tunable transition-metal-free aerobic oxidation of pyrazol-5-ones preparing either 4-hydroxypyrazoles (via C-H hydroxylation) or bispyrazoles (via dehydrogenative homocoupling) is described. The K 2 CO 3 /dioxane reagent system predominately promoted hydroxylation to deliver the α-hydroxylated pyrazoles. In contrast, the formation of bispyrazoles was overwhelmingly preferred with CH 3 CN as the reaction medium without any additives.

An aerobic oxidative aromatization of simple aliphatic alcohols and anilines under the Pd(OAc) 2 /2,4,6-Collidine/Brønsted acid catalytic system has been established, providing a direct approach for the preparation of diverse substituted quinoline derivatives in high yields with wide functional group tolerance. Practically, the protocol can be easily scaled up to gram-scale and was utilized in the concise formal synthesis of a promising herbicide candidate.

A highly enantioselective regiodivergent addition of alkoxyallenes to pyrazolones was developed to afford multiply functionalized alkylated products bearing a quaternary carbon stereocenter in high yields with excellent stereoselectivities. One approach is enabled by palladium catalysis, thus leading to branched allylic pyrazol-5-ones under mild reaction conditions. The other is catalyzed by a chiral Brønsted acid to give linear products exclusively. Moreover, the usefulness of this new method was highlighted by converting the allylic products into other interesting multifunctionalized pyrazolone derivatives which would be of great potential for the exploitation of pharmaceutically important molecules., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A practical and concise protocol for the efficient preparation of pyrrolo[1,2-a]quinoxalines through a cascade of alcohol oxidation/imine formation/intramolecular cyclization/oxidative dehydrogenation has been established. A series of substituted pyrrolo[1,2-a]quinoxaline derivatives were constructed readily in yields of 53-93% from the cheap primary alcohols by using dioxygen as the terminal oxidant. Remarkably, the fact that no extra metals and additives were necessary makes this unprecedented aerobic oxidation process highly step- and atom-economical. The usefulness of this transformation was further demonstrated with the gram-scale synthesis of compound 3aa under standard conditions.

A new approach has been established for Rh(iii)-catalyzed direct aza oxidative cyclization of non-prefunctionalized azobenzenes to provide 2-aryl-2H-benzotriazoles in good yields, in which AgNO3 instead of conventional azide reagents for the first time functions as the nitrogen source for the nitrogenation reaction. Preliminary mechanistic studies suggest that the Rh(iii)-catalyst could account for the nitration reaction, and subsequently cationic silver species might both play a vital role in the fission of the nitrogen-oxygen bonds in nitro groups and promote aza oxidative cyclization.

A new approach was developed for Pd(II)-catalyzed aromatic coupling of oxabenzonorbornadienes with triarylphosphines as both ligands and aryl donors. Diverse functional groups including halo- (F-, Cl-, and Br-), CF3(-), and furyl groups are well tolerated. For unsymmetrical triarylphosphines, the migration ability of aryls is consistent with the electronic property of substituents and maintains the order EDG-Ar > H-Ar > EWD-Ar (EDG means electron-donating group, EWG means electron-withdrawing group). A preliminary mechanistic study was also disclosed.