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Organic Letters

Xiao-Yang Chen, Seyma Ozturk, Erik J Sorensen
The first synthesis of substituted fluorenones directly from benzaldehydes and aryl iodides via a Pd(II)-catalyzed C(sp(2))-H functionalization cascade is reported. Featuring anthranilic acid as an inexpensive transient directing group, the process is compatible with a variety of benzaldehydes and aryl iodides. A three-step synthesis of the antiviral drug Tilorone was completed in an excellent overall yield (40%), demonstrating the utility of this method.
February 22, 2017: Organic Letters
Guo-Fu Zhang, Yue Li, Xiao-Qiang Xie, Cheng-Rong Ding
An efficient and direct ruthenium-catalyzed regioselective hydroxymethylation of (hetero)arenes via C-H activation with paraformaldehyde as a hydroxymethylating reagent is described. The corresponding products can be obtained in good to excellent yield. A number of aryl aldehydes can also be used in place of paraformaldehyde giving the desired alcohol products with similarly good results.
February 22, 2017: Organic Letters
Anupam Jana, Karol Grela
No abstract text is available yet for this article.
February 22, 2017: Organic Letters
Fei Ye, Mansour Haddad, Virginie Ratovelomanana-Vidal, Véronique Michelet
A novel, efficient, and mild synthetic route for the preparation of 2-aminopyridines via ruthenium-mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and cyanamides has been developed. This atom-economical catalytic process demonstrated remarkable regioselectivities to access pyridine derivatives of high synthetic utility.
February 22, 2017: Organic Letters
Seung Wook Kim, Wonchul Lee, Michael J Krische
Glycidols prepared via Sharpless asymmetric epoxidation participate in asymmetric redox-neutral carbonyl allylation with good levels of catalyst-directed diastereoselectivity. Equally stereoselective allylations may be performed from the aldehyde oxidation level using 2-propanol as the terminal reductant. An epoxide ring-opening reaction using AlMe3-n-BuLi is used to prepare the propionate-based stereotetrad spanning C17-C23 of dictyostatin, illustrating how this method may be applied to polyketide construction...
February 21, 2017: Organic Letters
Jean Wilfried Fredy, Jérémy Scelle, Gregory Ramniceanu, Bich-Thuy Doan, Célia S Bonnet, Éva Tóth, Mickaël Ménand, Matthieu Sollogoub, Guillaume Vives, Bernold Hasenknopf
A versatile, five-component, one-pot synthesis of cyclodextrin (CD) [3]rotaxanes using copper-catalyzed azide-alkyne cycloaddition has been developed. Head-to-head [3]rotaxanes of α-CD selectively functionalized by one or two gadolinium 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid monoamide complexes were obtained mechanostereoselectively. The magnetic resonance imaging efficiency, expressed by the longitudinal proton relaxivity of the rotaxanes, was significantly improved as compared to the functionalized CD...
February 21, 2017: Organic Letters
Xu Chen, Zhaoyang Cheng, Zhan Lu
A highly Markovnikov-selective, iron-catalyzed hydroboration of styrenes is reported using available oxazolinylphenyl picolinamide as the ligand to afford the branched hydroboration products with up to >50/1 b/l. This reaction is operationally simple and could be carried out in gram scale.
February 21, 2017: Organic Letters
Komala Pandurangan, Anna B Aletti, Devis Montroni, Jonathan A Kitchen, Miguel Martínez-Calvo, Salvador Blasco, Thorfinnur Gunnlaugsson, Eoin M Scanlan
A facile one-pot synthesis of 3-amino-[1,2,4]-triazolo[4,3-a]pyridines from thiosemicarbazides through anion mediated synthesis is reported. Thiosemicarbazides derived from 2-hydrazino pyridine, 5-chloro 2-hydrazino pyridine, and 2-hydrazine quinoline were formed in situ as anion receptors in the presence of TBAF. Under microwave heating, thiosemicarbazides furnished the triazolo pyridines in good to moderate yields. The formation of the thiosemicarbazides hydrogen bonding anion receptors was critical in cascading the reaction toward the formation of the triazolo pyridines...
February 21, 2017: Organic Letters
Ajay L Chandgude, Alexander Dömling
The Ugi four-component reaction (U-4CR) with N-hydroxyimides as a novel carboxylic acid isostere has been reported. This reaction provides straightforward access to α-hydrazino amides. A broad range of aldehydes, amines, isocyanides and N-hydroxyimides were employed to give products in moderate to high yields. This reaction displays N-N bond formation by cyclic imide migration in the Ugi reaction. Thus, N-hydroxyimide is added as a new acid component in the Ugi reaction and broadens the scaffold diversity.
February 21, 2017: Organic Letters
Yi-Jin Li, Na Yan, Chun-Hua Liu, Yang Yu, Yu-Long Zhao
A new strategy for direct and highly efficient synthesis of 2,3'-bisindolin-3-ones has been developed via a gold/copper-co-catalyzed tandem reactions of 2-alkynylanilines using TBHP as the terminal oxidant and oxygen-atom source. The single-step process involves a novel tandem intermolecular nucleophilic addition, intramolecular cyclization/oxidative cross-dehydrogenative coupling where up to four new bonds and two indole rings were created simultaneously in one-pot manner. The reaction features a broad substrate scope, good functional group tolerance, and high atom-economy...
February 20, 2017: Organic Letters
Ju Hyun Kim, Taemoon Song, Young Keun Chung
A highly regioselective rhodium-catalyzed intermolecular carbonylative [2 + 2 + 1] cycloaddition of alkynes using alcohol as a CO surrogate to access 4-methylene-2-cyclopenten-1-ones has been developed. In this transformation, the alcohol performs multiple roles, including generating the Rh-H intermediate, functioning as the CO source, and assisting in the isomerization of the alkyne. Alkynes can act as both the olefin and the alkyne partner in the cyclopentenone core.
February 20, 2017: Organic Letters
Cheng Tao, Jing Zhang, Xiaoming Chen, Huifei Wang, Yun Li, Bin Cheng, Hongbin Zhai
The tricyclic intermediate 2 has been synthesized in eight steps from known compound 6 in 20% overall yield. As such, this constitutes a highly efficient formal synthesis of (±)-aplykurodinone-1. This synthesis features a unique, one-pot, intramolecular hetero-Pauson-Khand reaction (h-PKR)/desilylation sequence to expeditiously construct the tricyclic framework, providing valuable insights for expanding the scope and boundaries of h-PKR.
February 20, 2017: Organic Letters
Min Zhang, Jimei Liu, Ridao Chen, Jinlian Zhao, Kebo Xie, Dawei Chen, Keping Feng, Jungui Dai
Furanharzianones A and B (2 and 3), two new harziane-type diterpenoids with a tetrahydrofuran and unusual 4/7/5/6/5 ring system, were obtained from the microbial transformation of harzianone (1) by a bacterial strain Bacillus sp. IMM-006. The structures, including the stereochemistry, of the two new compounds were elucidated by extensive spectroscopic analysis. The absolute configuration of 2 was unambiguously determined by single-crystal X-ray diffraction. In addition, a plausible bioconversion pathway was proposed...
February 20, 2017: Organic Letters
Shuyao Zhang, Beiming Cheng, Shen-An Wang, Ling Zhou, Chen-Ho Tung, Jianwu Wang, Zhenghu Xu
An unprecedented gold-catalyzed cycloisomerization/1,5-H migration/Diels-Alder reaction cascade has been developed that enables the rapid construction of complex nitrogen polycyclic compounds. This one-pot, three-step cascade reaction offers good yields of the products and is promoted by a single gold catalyst under very mild conditions.
February 20, 2017: Organic Letters
Rylan M W Wolfe, John R Reynolds
The synthesis of thienopyrroledione (TPD) has been updated to reduce the number of synthetic steps, remove hazardous and toxic reagents, reduce the amount of byproduct waste, and reduce the use of solvents when unnecessary. Diverse functionalization is possible, introducing 16 examples in yields from 34% to 95%. This reaction scheme was shown to be general for thiophene imides, and a more thorough exploration into side chain engineering is presented with TPD acceptors often used in organic electronic applications...
February 20, 2017: Organic Letters
Zhongyi Zeng, Hongming Jin, Jin Xie, Bing Tian, Matthias Rudolph, Frank Rominger, A Stephen K Hashmi
A novel and atom-economical synthesis of fully substituted 4-aminoimidazoles via gold-catalyzed selective [3 + 2] annulation of 1,2,4-oxadiazoles with ynamides is reported. This protocol represents a new strategy to access α-imino gold carbenes, which corresponds to an unprecedented intermolecular transfer of N-acylimino nitrenes to ynamides. Moreover, the reaction proceeds with 100% atom economy, exhibits good functional group tolerance, and can be conducted in gram scale.
February 20, 2017: Organic Letters
Valquírio G Correia, Juliana C Abreu, Caio A E Barata, Leandro H Andrade
A novel and highly efficient synthetic approach to pyrroloindolines has been developed. The process is based on tandem radical addition/cyclization with inexpensive iron catalyst. This method tolerates a wide range of N-methyl-N-arylacrylamides as well carbamoyl radicals, providing access to a variety of functionalized 3,3-disubstituted oxindoles, key intermediates for many bioactive pyrroloindolines such as (±)-esermethole, (±)-deoxyeseroline, and (±)-physovenol methyl ether.
February 20, 2017: Organic Letters
Jiapian Huang, Yangfei Huang, Tao Wang, Qin Huang, Zhihua Wang, Zhiyuan Chen
A microwave-assisted, Cp*Co(III)-catalyzed direct C-H activation/double C-N bond formation reaction of simple NH-sulfoximines with 1,4,2-dioxazol-5-ones to produce diverse thiadiazine-1-oxides is reported. The reaction tolerates a broad range of functional groups under external oxidant-free conditions and only releases CO2 and H2O as the sole byproducts. The preliminary mechanistic studies revealed an electrophilic metalation pathway is likely involved in the reaction.
February 17, 2017: Organic Letters
Imran Kazi, Somraj Guha, Govindasamy Sekar
CBr4 has been employed as a halogen bond donor catalyst for the selective activation of aldehyde, to achieve an efficient solvent- and metal-free C═C bond forming reaction in the presence of strong acid sensitive groups such as methoxy, cyanide, ester, and ketal for the synthesis of α,β-unsaturated ketones. This unique capability of CBr4 to act as a halogen bond donor has been explored and established using UV-vis as well as IR spectroscopy. Moreover, this unprecedented methodology enables the synthesis of the pharmaceutically important molecule licochalcone A...
February 17, 2017: Organic Letters
Xiao-Yun Li, Wen-Qiang Yuan, Sheng Tang, Yi-Wei Huang, Jia-Hui Xue, Li Na Fu, Qi-Xiang Guo
A highly efficient alkenylation reaction of arylglyoxals with 3-vinylindoles catalyzed by chiral calcium phosphate is described. Structurally diverse allylic alcohols bearing indole and carbonyl units are prepared in excellent yields, good diastereoselectivities, and high to excellent enantioselectivities. These products are good building blocks for the synthesis of polysubstituted chiral tetrahydrocarbozol-2-ones. The mechanism study indicates that the most likely role of the catalyst is to activate the hydrate of arylglyoxal and control the stereoselectivity via desymmetric coordination...
February 17, 2017: Organic Letters
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