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Organic Letters

Luis Bering, Felix M Paulussen, Andrey P Antonchick
The nitrosonium ion-catalyzed dehydrogenative coupling of heteroarenes under mild reaction conditions is reported. The developed method utilizes ambient molecular oxygen as a terminal oxidant, and only water is produced as byproduct. Dehydrogenative coupling of heteroarenes translated into the rapid discovery of novel hedgehog signaling pathway inhibitors, emphasizing the importance of the developed methodology.
March 16, 2018: Organic Letters
Robert M B Dyer, Philip L Hahn, Michael K Hilinski
The first examples of nonenzymatic N-oxidation of heteroarenes in the presence of amines are reported. Pyridine, quinoline, and isoquinoline N-oxides are selectively formed in the presence of more reactive aliphatic and alicyclic amines by use of an in situ protonation strategy and an iminium salt organocatalyst. Application to late-stage functionalization that mimics phase 1 metabolism of small-molecule drugs is also demonstrated.
March 16, 2018: Organic Letters
Thomas Hostier, Zeina Neouchy, Vincent Ferey, Domingo Gomez Pardo, Janine Cossy
A nickel-catalyzed cross-coupling of alkenyl methyl ethers with Grignard reagents, under mild conditions, is described. These conditions allowed access to various stilbenes and heterocyclic stilbenic derivatives as well as to a potential anticancer agent DMU-212.
March 15, 2018: Organic Letters
Zhihong Li, Rong Huang, Hongtao Xu, Jiakang Chen, Yuexiong Zhan, Xianhao Zhou, Hongli Chen, Biao Jiang
No abstract text is available yet for this article.
March 15, 2018: Organic Letters
Qi-Wei Zhang, Jaroslav Zajíček, Bradley D Smith
A [1]rotaxane with two threaded α-cyclodextrin (α-CD) wheels was synthesized in 92% yield using a one-pot process at room temperature that employed spontaneous α-CD threading onto a 12-carbon alkyl chain in water followed by an oxime condensation reaction that attached two boronic acid-containing stopper groups. Rapid pirouetting of the threaded α-CD wheels around the encapsulated dumbbell was switched "ON" or "OFF" by the presence of chemical additives that controlled boronate ester bond formation between the interlocked components...
March 15, 2018: Organic Letters
Guisheng Li, Olga V Zatolochnaya, Xiao-Jun Wang, Sonia Rodríguez, Bo Qu, Jean-Nicolas Desrosiers, Hari P R Mangunuru, Soumik Biswas, Daniel Rivalti, Shuklendu D Karyakarte, Joshua D Sieber, Nelu Grinberg, Ling Wu, Heewon Lee, Nizar Haddad, Daniel R Fandrick, Nathan K Yee, Jinhua J Song, Chris H Senanayake
Novel bidentate phosphine ligands BABIPhos featuring a biaryl bis-dihydrobenzooxaphosphole core are presented. Their synthesis was achieved via Pd-catalyzed reductive homocoupling of dihydrobenzooxaphosphole aryl triflates. An efficient route toward various analogues was also established, giving access to phosphines with different electronic and steric properties. The newly obtained ligands demonstrated high efficiency and selectivity in Rh-catalyzed asymmetric hydrogenation of di- and trisubstituted enamides...
March 15, 2018: Organic Letters
Hao Chen, Xuehe Lu, Xuejian Xia, Qiongqiong Zhu, Yanhong Song, Jie Chen, Weiguo Cao, Xiaoyu Wu
A decarboxylative formal [4 + 2] cycloaddition reaction between ethynyl benzoxazinanones and 5-substituted 2-silyloxyfurans catalyzed by chiral Cu-Pybox complex is described. This method allows the formation of intriguing tetrahydroquinolines fused with a butyrolactone moiety featuring three contiguous chiral centers in high yields with excellent diastereo- and enantioselectivities in most cases. The utility of this method was exemplified by the removal of the N-protecting groups and derivatization on the terminal alkyne functionality of the cyclization products...
March 14, 2018: Organic Letters
Khrystofor Khokhlov, Nathaniel J Schuster, Fay Ng, Colin Nuckolls
Molecular building blocks are designed and created for the cis- and trans-dibrominated perylenediimides. The syntheses are simple and provide these useful materials on the gram scale. To demonstrate their synthetic versatility, these building blocks were used to create new dimeric perylenediimide helixes. Two of these helical dimers are twistacenes, and one is a helicene. Crucially, each possesses regiochemically defined functionality that allows the dimer helix to be elaborated into higher oligomers. It would be very difficult to prepare these helical PDI building blocks regioselectively without the methods described...
March 14, 2018: Organic Letters
He-Min Wang, Hao Zhou, Qing-Song Xu, Tai-Shang Liu, Chen-Lu Zhuang, Mei-Hua Shen, Hua-Dong Xu
A t-BuOCu-initiated reaction sequence of styrene borometalation and intramolecular imine addition has been achieved using a Cu(OTf)2 /dppf combination as catalyst. The product of this reaction cascade is a useful 2,3-disubstituted indoline bearing a versatile boryl moiety and is formed with sole cis-selectivity. To account for the observation of the exclusive formation of cis-stereoisomers, a transition state featuring copper-imine coordination is suggested. The application to the synthesis of antioxidant tetrahydroindenoindoles is described...
March 14, 2018: Organic Letters
Shuang Luo, Zhuang Xiong, Yongzhi Lu, Qiang Zhu
A highly efficient synthesis of planar chiral pyrido[3,4- b] ferrocenes by a palladium-catalyzed enantioselective isocyanide insertion/desymmetric C(sp2 )-H bond activation reaction was developed. Various planar chiral pyridoferrocenes were obtained in high yields with good to excellent enantioselectivity under mild conditions (up to 99% yield, 99% ee), enabled by a unique SPINOL-derived phosphoramidite ligand.
March 14, 2018: Organic Letters
Hirofumi Maekawa, Katsuaki Noda, Keisuke Kuramochi, Tianyuan Zhang
Vinylsilanes were directly prepared from the corresponding vinyl triflates under magnesium-promoted reductive conditions in THF with no transition metal catalyst, and gem-bis-silylated compounds were obtained in NMP. Investigation of the redox potential of starting materials and products suggested that reductive coupling reactions of vinyl triflates might be controlled by the reduction potential. A variety of gem-bis-silylated compounds and 3-silyladipic acid esters were easily synthesized in only two steps from vinyl triflates in high yields...
March 14, 2018: Organic Letters
Marcus Reitti, Ramani Gurubrahamam, Melanie Walther, Erik Lindstedt, Berit Olofsson
Two transition-metal-free methods to access substituted phenols via the arylation of silanols or hydrogen peroxide with diaryliodonium salts are presented. The complementary reactivity of the two nucleophiles allows synthesis of a broad range of phenols without competing aryne formation, as illustrated by the synthesis of the anesthetic Propofol. Furthermore, silyl-protected phenols can easily be obtained, which are suitable for further transformations.
March 14, 2018: Organic Letters
Sushovan Paladhi, In-Soo Hwang, Eun Jeong Yoo, Do Hyun Ryu, Choong Eui Song
A practical and highly enantioselective nonenzymatic kinetic resolution of racemic β-hydroxy carbonyl (aldol) compounds through enantioselective dehydration process was developed using a cation-binding Song's oligoethylene glycol (oligoEG) catalyst with potassium fluoride (KF) as base. A wide range of racemic aldols was resolved with extremely high selectivity factors ( s = up to 2393) under mild reaction conditions. This protocol is easily scalable. It provides an alternative approach for the syntheses of diverse biologically and pharmaceutically relevant chiral aldols in enantiomerically pure form...
March 14, 2018: Organic Letters
Adam A Rajkiewicz, Marcin Kalek
An organocatalyzed metal-free, direct olefination of aldehydes with vinyliodonium salts has been achieved by an N-heterocyclic carbene-promoted C-H bond activation. The reaction proceeds under very mild conditions, delivering a range of (hetero)aryl-vinyl ketones in good yields. The retention of the double bond configuration is uniformly observed, and the application of 2-methoxyphenyl auxiliary group in iodonium salts secures a complete selectivity of the vinyl transfer.
March 14, 2018: Organic Letters
Yishu Bao, Xiuqin Yang, Qingfa Zhou, Fulai Yang
A highly regio- and stereoselective synthesis of β-haloalkenyl sulfides using commercially available ketones and sulfonyl hydrazides as starting materials has been developed. This protocol obviates the need for alkynes and traditional sulfenylating agents and therefore opens up a new door to construct β-iodoalkenyl sulfides in a highly simple manner. This study reveals that ketones could be used as vinyl iodide precursors in organic synthesis.
March 14, 2018: Organic Letters
Meng-Hua Wang, You-Cai Hu, Bing-Da Sun, Meng Yu, Shu-Bin Niu, Zhe Guo, Xiao-Yan Zhang, Tao Zhang, Gang Ding, Zhong-Mei Zou
The highly photosensitive characteristic of poly-sulfide chetomins was first unveiled, and four new unstable analogues, chetomins A-D (1-4), with significant cytotoxicity were successfully purified in darkness. The visible-light-induced desulfurization and intermolecular disproportionation were revealed to initiate the interconversion of chetomin analogues, which explained the long-recognized puzzle of rarity and instability of chetomin analogues.
March 14, 2018: Organic Letters
Chi-Hao Chang, Chih-Ming Chou
This study explores a Pd-catalyzed decarboxylative Heck-type Csp3 -Csp2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.
March 14, 2018: Organic Letters
Meng-Yang Chang, Yan-Shin Wu, Han-Yu Chen
A concise, one-pot synthesis of sulfonyl benzofuran-3-ones and chroman-4-ones from α-sulfonyl o-hydroxyacetophenones is described, using a combination of K2 CO3 , CuI, and dimethylsulfoxide (DMSO). This annulation protocol generates one carbon-oxygen (C-O) bond and one carbon-carbon (C-C) bond in a highly efficient manner.
March 14, 2018: Organic Letters
Jun Zheng, Bernhard Breit
A palladium-catalyzed intermolecular direct C-H allylation of polyfluoroarenes with alkynes is reported. Unlike classic hydroarylation reactions, alkynes are used as allylic electrophile surrogates in this direct aromatic C-H allylation. As an atom-economic and efficient method, various linear allylated fluoroarenes were synthesized from two simple and easy-to-access feedstocks in good to excellent yields, as well as regio- and stereoselectivity.
March 14, 2018: Organic Letters
Chun-Yan Wu, Yu-Fang Zhang, Ming-Hua Xu
A site-selective rhodium-catalyzed asymmetric 1,4-/1,2-addition of arylboronic acids to challenging α,β-unsaturated cyclic ketimines was realized through a ligand-controlled strategy. By employing different chiral olefin ligands, a ligand-controlled switch in the reaction regioselectivity was attained for the first time. The reactions allow the synthesis of highly valuable α,α-disubstituted chiral allylic amines and enantioenriched 1,4-adducts. Further product transformation provided easy access to various quaternary carbon-containing chiral amines and amino acid derivatives bearing multifunctional groups...
March 13, 2018: Organic Letters
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