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Heterocyclic chemistry

Tobias Böttcher, Daniel Himmel, Jan Schröder
Herein we present a convenient one-pot route to a sterically demanding superbasic pyridine. Functionalization of the 2,6-positions with the highly sigma-donating boryl-groups shifts the calculated gas phase basicity of the pyridine's nitrogen atom to 1012 kJ mol-1, which outperforms the 'proton sponge' 1,8-bis(dimethylamino)naphthalene (996 kJ mol-1). The diazaboryl groups are oriented orthogonal to the pyridine ring and do not block the N-position, resembling the geometry of commonly used N-heterocyclic carbenes...
June 23, 2017: Chemistry: a European Journal
Yu-Feng Liang, Ning Jiao
The selective oxidation of organic molecules is a fundamentally important component of modern synthetic chemistry. In the past decades, direct oxidative C-H and C-C bond functionalization has proved to be one of the most efficient and straightforward methods to synthesize complex products from simple and readily available starting materials. Among these oxidative processes, the use of molecular oxygen as a green and sustainable oxidant has attracted considerable attention because of its highly atom-economical, abundant, and environmentally friendly characteristics...
June 21, 2017: Accounts of Chemical Research
Xi Wang, Armido Studer
The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C-CF3, X-CF3 (X = heteroatom), C-Rf (Rf = perfluoroalkyl), X-Rf, C-N3, C-CN, S-CN, and C-X bonds...
June 21, 2017: Accounts of Chemical Research
Hidayat Hussain, Ivan R Green
Isocoumarins comprise a six-membered oxygen heterocycle (α-pyranone) along with one aromatic ring and are known to possess interesting biological properties. During the last two decade (1997-2016), isocoumarin chemistry has attracted attention due to its biological and pharmaceutical effects viz., anticancer, anti-diabetic, antibacterial, antimalarial, and fungicidal effects. Areas covered: This review covers the patents on the therapeutic activities of natural and synthetic isocoumarins over the last two decades (1997-2016)...
June 16, 2017: Expert Opinion on Therapeutic Patents
Luis M Martínez-Prieto, Lena Rakers, Angela M López-Vinasco, Israel Cano, Yannick Coppel, Karine Philippot, Frank Glorius, Bruno Chaudret, Piet W N M van Leeuwen
Soluble platinum nanoparticles (Pt NPs) ligated by two different long-chain N-Heterocyclic Carbenes (LC-IPr and LC-IMe) were synthesized and fully characterized by TEM, HRTEM, WAXS, XPS and solution NMR. The surface chemistry of these NPs (Pt@LC-IPr and Pt@LC-IMe) was investigated by FT-IR and solid state NMR using CO as a probe molecule. A clear influence of the bulkiness of the N-substituents was observed on the size, surface state and catalytic activity of these Pt NPs. While Pt@LC-IMe showed no activity in the hydroboration of phenylacetylene, Pt@LC-IPr revealed good selectivity for the trans-isomer which might be supported by a homogeneous species...
June 14, 2017: Chemistry: a European Journal
David E Lewis
Tutor, journalist, patriot, and defector: Aleksei Yevgen'evich Chichibabin made seminal contributions to the chemistry of pyridines. As the Chichibabin reaction enters its second century, it is appropriate to re-examine the life of this remarkable chemist and his legacy to heterocyclic chemistry.
June 12, 2017: Angewandte Chemie
Saurabh Sunil Chitnis, Hazel A Sparkes, Vincent T Annibale, Natalie E Pridmore, Alex M Oliver, Ian Manners
We report the addition of a cyclotriphosphine to a broad range of nitriles giving access to the first examples of free 1-aza-2,3,4-triphospholenes in a rapid, ambient temperature, one-pot, high-yield protocol. The reaction produces electron-rich heterocycles (four lone pairs) and features homoatomic σ-bond heterolysis, thereby combining the key features of the 1,3-dipolar cycloaddition chemistry of azides and cyclopropanes. We also report the first catalytic addition of P-P bonds to the CN triple bond. The coordination chemistry of the new heterocycles is explored...
June 12, 2017: Angewandte Chemie
Bruno Commare, Etienne Schmitt, Fallia Aribi, Armen Panossian, Jean-Pierre Vors, Sergiy Pazenok, Frédéric R Leroux
Fluorinated heterocycles are important building blocks in pharmaceutical, agrochemical and material sciences. Therefore, organofluorine chemistry has witnessed high interest in the development of efficient methods for the introduction of emergent fluorinated substituents (EFS) onto heterocycles. In this context, fluoroalkyl amino reagents (FARs)-a class of chemicals that was slightly forgotten over the last decades-has emerged again recently and proved to be a powerful tool for the introduction of various fluorinated groups onto (hetero)aromatic derivatives...
June 12, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Donglu Xiong, Wenxi Zhou, Zhiwu Lu, Suping Zeng, Jun Joelle Wang
The chromanone scaffold is a privileged structure in heterocyclic chemistry and drug discovery. A highly efficient copper-catalyzed asymmetric conjugated reduction of chromones is developed to give chiral chromanones with good yields (80-99%) and excellent ee values (94->99% ee). Particularly noteworthy is that chiral thiochromanones are also constructed using this method in 74-87% yields with 96-97% ee. The established asymmetric synthesis paves the way for their further pharmaceutical studies.
June 22, 2017: Chemical Communications: Chem Comm
Jie Li, Korkit Korvorapun, Suman De Sarkar, Torben Rogge, David J Burns, Svenja Warratz, Lutz Ackermann
The full control of positional selectivity is of prime importance in C-H activation technology. Chelation assistance served as the stimulus for the development of a plethora of ortho-selective arene functionalizations. In sharp contrast, meta-selective C-H functionalizations continue to be scarce, with all ruthenium-catalysed transformations currently requiring difficult to remove or modify nitrogen-containing heterocycles. Herein, we describe a unifying concept to access a wealth of meta-decorated arenes by a unique arene ligand effect in proximity-induced ruthenium(II) C-H activation catalysis...
June 9, 2017: Nature Communications
Jun Xuan, Armido Studer
Carbo- and heterocycles are widely found in natural products, biologically active structures, medicinally relevant compounds, and in many other fine chemicals. The development of novel, general and efficient methods for their construction has therefore gained great interest in synthetic organic chemistry. Recently, radical chemistry has become a heavily investigated research field (a renaissance!). Along these lines, radical cascade cyclization of 1,n-enynes and diynes has emerged as a powerful strategy for the preparation of carbo- and heterocycles...
June 6, 2017: Chemical Society Reviews
Karolina Kwapien, Mirna Damergi, Serge Nader, Léa El Khoury, Zeina Hobaika, Richard G Maroun, Jean-Philip Piquemal, Laurent Gavara, Dorothée Berthomieu, Jean-François Hernandez, Nohad Gresh
In the context of the SIBFA polarizable molecular mechanics/dynamics (PMM/PMD) procedure, we report the calibration and a series of validation tests for the 1,2,4-triazole-3-thione (TZT) heterocycle. TZT acts as the chelating group of inhibitors of dizinc metallo-β-lactamases (MBL), an emerging class of Zn-dependent bacterial enzymes, which by cleaving the β-lactam bond of most β-lactam antibiotics are responsible for the acquired resistance of bacteria to these drugs. Such a study is indispensable prior to performing PMD simulations of complexes of TZT-based inhibitors with MBL's, on account of the anchoring role of TZT in the dizinc MBL recognition site...
June 22, 2017: Journal of Physical Chemistry. B
Chisato Mukai
Some recent results on the development of new and reliable procedures for the construction of diverse ring systems based on the chemistry of sp-hybridized species, especially allene functionality, are described. This review includes: (i) synthesis of the multi-cyclic skeletons by combination of the π-component of allene with suitable other π-components such as alkyne, alkene, or additional allene under Rh-catalyzed conditions; (ii) synthesis of heterocycles as well as carbocycles by reaction of the sp-hybridized center of allene with some nucleophiles in an endo-mode manner; and (iii) total syntheses of natural products and related compounds from the sp-hybridized starting materials...
2017: Chemical & Pharmaceutical Bulletin
Petra Schneider, Gisbert Schneider
Privileged structures inspire compound library design in medicinal chemistry. We performed a comprehensive analysis of 1.4 million bioactive compounds, with the aim of assessing the prevalence of certain molecular frameworks. We used the Shannon entropy formalism to quantify the promiscuity of the most frequently observed atom scaffolds across the annotated target families. This analysis revealed an apparent inverse relationship between hydrogen-bond-acceptor count of a scaffold and its potential promiscuity...
June 26, 2017: Angewandte Chemie
Makafui Gasonoo, Akinari Sumita, Kenneth N Boblak, Kristen Giuffre, Tomohiko Ohwada, Douglas A Klumpp
A superacid-promoted method for the synthesis of 9,9-diarylfluorenes is described. The chemistry involves cyclizations and arylations with biphenyl-substituted heterocyclic ketones and a mechanism is proposed involving superelectrophilic intermediates. The key reactive intermediates-dicationic and trication fluorenyl cations have been observed by low-temperature NMR and the mechanism has been further studied using DFT calculations.
June 6, 2017: Journal of Organic Chemistry
Neelima Shrivastava, Mohd Javed Naim, Md Jahangir Alam, Farah Nawaz, Shujauddin Ahmed, Ozair Alam
Cancer, also known as malignant neoplasm, is a dreadful disease which involves abnormal cell growth having the potential to invade or spread to other parts of the body. Benzimidazole is an organic compound that is heterocyclic and aromatic in nature. It is a bicyclic compound formed by the fusion of the benzene and imidazole ring systems. It is an important pharmacophore and a privileged structure in medicinal chemistry. According to the World Health Organisation (2015 survey), one in six deaths is due to cancer around the globe, accounting for 8...
June 2017: Archiv der Pharmazie
Ewa Erdmann, Marie-Christine Bacchus-Montabonel, Marta Łabuda
Investigations of collision-induced processes involving carbon ions and molecules of biological interest, in particular DNA building blocks, are crucial to model the effect of radiation on cells in order to improve medical treatments for cancer therapy. Using carbon ions appears to be one of the most efficient ways to increase biological effectiveness to damage cancerous cells by irradiating deep-seated tumors. Therefore, interest in accurate calculations to understand fundamental processes occurring in ion-molecule collision systems has been growing recently...
May 25, 2017: Physical Chemistry Chemical Physics: PCCP
Hidetoshi Noda, Makoto Furutachi, Yasuko Asada, Masakatsu Shibasaki, Naoya Kumagai
The expansion of molecular diversity beyond what nature can produce is a fundamental objective in chemical sciences. Despite the rich chemistry of boron-containing heterocycles, the 1,3-dioxa-5-aza-2,4,6-triborinane (DATB) ring system, which is characterized by a six-membered B3NO2 core, remains elusive. Here, we report the synthesis of m-terphenyl-templated DATB derivatives, displaying high stability and peculiar Lewis acidity arising from the three suitably arranged boron atoms. We identify a particular utility for DATB in the dehydrative amidation of carboxylic acids and amines, a reaction of high academic and industrial importance...
June 2017: Nature Chemistry
Liu-Zhu Yu, Kai Chen, Zi-Zhong Zhu, Min Shi
During the past several years, functionalized alkylidenecyclopropanes (FACPs) have attracted intensive attention in synthetic chemistry. Many interesting transformations of FACPs have been developed to synthesize a lot of structurally diverse and valuable polycyclic and heterocyclic compounds. This review will classify FACPs into aryl-FACPs, alkyl-FACPs and ring-FACPs for the first time, and recent interesting chemical transformations in these research fields will be included, respectively, from 2011. Moreover, we will pay more attention to the clarification of the reaction mechanism, in which the C-C bond cleavage of alkylidenecyclopropanes (ACPs) will be emphasized...
May 17, 2017: Chemical Communications: Chem Comm
Alberto Hernán-Gómez, Alan R Kennedy, Eva Hevia
Combining alkali-metal-mediated metalation (AMMM) and N-heterocyclic carbene (NHC) chemistry, a novel C-N bond activation and ring-opening process is described for these increasingly important NHC molecules, which are generally considered robust ancillary ligands. Here, mechanistic investigations on reactions of saturated NHC SIMes (SIMes=[:C{N(2,4,6-Me3 C6 H2 )CH2 }2 ]) with Group 1 alkyl bases suggest this destructive process is triggered by lateral metalation of the carbene. Exploiting co-complexation and trans-metal-trapping strategies with lower polarity organometallic reagents (Mg(CH2 SiMe3 )2 and Al(TMP)iBu2 ), key intermediates in this process have been isolated and structurally defined...
June 1, 2017: Angewandte Chemie
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