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Organic Letters

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https://www.readbyqxmd.com/read/28937777/co-catalyzed-c-sp-3-h-oxidative-coupling-of-glycine-and-peptide-derivatives
#1
Marcos San Segundo, Itziar Guerrero, Arkaitz Correa
Cobalt-catalyzed selective α-alkylation and α-heteroarylation processes of α-amino esters and peptide derivatives are described. These cross-dehydrogenative reactions occur under mild conditions and allow for the rapid assembly of structurally diverse α-amino carbonyl compounds. Unlike enolate chemistry, these methods are distinguished by their site-specificity, occur without racemization of the existing chiral centers, and exhibit total selectivity for aryl glycine motifs over other amino acid units, hence providing ample opportunities for peptide modifications...
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937770/correction-to-sulfonyl-imidazolium-salts-as-reagents-for-the-rapid-and-efficient-synthesis-of-nucleoside-polyphosphates-and-their-conjugates
#2
Samy Mohamady, Ahmed Desoky, Scott D Taylor
No abstract text is available yet for this article.
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937768/lewis-acid-mediated-cascade-friedel-craft-alkyne-indol-2-yl-cation-cyclization-vinyl-cation-trapping-for-the-synthesis-of-n-fused-indole-derivatives
#3
Santosh J Gharpure, Yogesh G Shelke
A Lewis acid promoted cascade Friedel-Craft/alkyne indol-2-yl cation cyclization/vinyl cation trapping for an efficient and divergent synthesis of N-fused indoles is developed. The present study illustrates the first example of an alkyne as a nucleophile on the less explored indol-2-yl cation. The method efficiently affords pharmaceutically important pyrrolizino-quinolines and complex fused indole derivatives in high yields.
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937766/approach-toward-the-understanding-of-coupling-mechanism-for-edc-reagent-in-solvent-free-mechanosynthesis
#4
Aneta Wróblewska, Piotr Paluch, Ewelina Wielgus, Grzegorz Bujacz, Marta K Dudek, Marek J Potrzebowski
A unique approach in mechanosynthesis, joining solid-state NMR spectroscopy, X-ray crystallography, and theoretical calculations, is employed for the first time to study the mechanism of the formation of the C-N amide bond using EDC·HCl as a coupling reagent. It has been proved that EDC·HCl, which in the crystal lattice exists exclusively in the cyclic form (X-ray data), easily undergoes transformation to a pseudocyclic stable intermediate in reaction with carboxylic acid forming a low-melt phase (differential scanning calorimetry, solid-state NMR)...
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937229/stereoselective-construction-of-%C3%AE-tetralone-fused-spirooxindoles-via-pd-catalyzed-domino-carbene-migratory-insertion-conjugate-addition-sequence
#5
Dhanarajan Arunprasath, Balasubramanian Devi Bala, Govindasamy Sekar
An efficient diastereoselective synthesis of α-tetralone-fused spirooxindoles is reported. The Pd-catalyzed domino reaction proceeds through a carbene migratory insertion followed by a 6-endo-trig mode of conjugate addition sequence from easily accessible isatin-derived N-tosylhydrazones and 2'-iodochalcones. The versatility of the protocol has been showcased by high functional group tolerance, broad substrate scope, and extension to an expedient synthesis of spiroacenaphthylenes. NMR reaction profiling and deuterium-labeling investigations provide insight into the mechanistic pathway...
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937228/modular-access-to-triarylethylene-units-from-arylvinyl-mida-boronates-using-a-regioselective-heck-coupling
#6
R N Khanizeman, E Barde, R W Bates, A Guérinot, J Cossy
A palladium-catalyzed, silver-mediated Heck coupling between arylvinyl MIDA boronate esters and aryl iodides is disclosed. The reaction provides an efficient and modular access to a range of 1,1-diaryl alkenyl MIDA boronates that can be easily transformed into triarylethylene compounds through a Suzuki coupling.
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28937223/iron-promoted-difunctionalization-of-alkenes-by-phenylselenylation-1-2-aryl-migration
#7
Ping Wu, Kaikai Wu, Liandi Wang, Zhengkun Yu
Iron-promoted difunctionalization of α,α-diaryl and α-aryl-α-alkyl allylic alcohols has been efficiently achieved by means of N-(phenylseleno)phthalimide (N-PSP) under mild conditions. An in situ generated phenylselenium cation (PhSe(+)) was added to the olefinic C═C bond to initiate the regioselective phenylselenylation with concomitant 1,2-aryl migration, following a migration preference contrary to the well-known radical pathway. Hydrazonation of the resultant alkene difunctionalization products, that is, α-aryl-β-phenylselenyl ketones, and subsequent copper-catalyzed dehydroselenylation efficiently afforded functionalized 2-pyrazoline derivatives...
September 22, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933860/stereoselective-synthesis-of-z-vinylsilanes-via-palladium-catalyzed-direct-intermolecular-silylation-of-c-sp-2-h-bonds
#8
Jin-Long Pan, Chao Chen, Zhi-Gang Ma, Jia Zhou, Li-Ren Wang, Shu-Yu Zhang
An efficient and convenient palladium-catalyzed direct intermolecular silylation of C(sp(2))-H bonds by using disilanes as the silicon source with the assistance of a readily removable bidentate directing group is reported. This strategy provided a regio- and stereoselective protocol for exclusive synthesis of Z-vinylsilanes with reasonable to excellent yields and good functional group compatibility. Silylation of the isolated palladacycle intermediate revealed the Z-stereoselective pathway. Moreover, the practicality and effectiveness of this method were illustrated by a gram-scale experiment and further functionalization of the silylation product...
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933859/copper-catalyzed-cascade-cyclization-of-1-7-enynes-toward-trifluoromethyl-substituted-1-h-spiro-azirine-2-4-quinolin-2-3-h-ones
#9
Qiang Meng, Fei Chen, Wei Yu, Bing Han
A novel method for the synthesis of trifluoromethyl-containing 1'H-spiro[azirine-2,4'-quinolin]-2'(3'H)-ones by a CF3-radical-triggered tandem reaction of benzene-linked 1,7-enynes is described. This protocol utilizes 1-trifluoromethyl-1,2-benziodoxole as the trifluoromethylating reagent and TMSN3 as the aminating reagent. By this method, various potentially bioactive trifluoromethylated 1'H-spiro[azirine-2,4'-quinolin]-2'(3'H)-ones were facilely synthesized via a radical cascade process.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933551/kinetic-benchmarking-reveals-the-competence-of-prenyl-groups-in-ring-closing-metathesis
#10
Karim A Bahou, D Christopher Braddock, Adam G Meyer, G Paul Savage
A series of prenyl-containing malonates are kinetically benchmarked against the standard allyl-containing congeners using a ruthenium benzylidene precatalyst for ring-closing metatheses. The prenyl grouping is found to be a superior acceptor olefin compared to an allyl group in RCM processes with ruthenium alkylidenes derived from terminal alkenes. The prenyl group is also found to be a highly competent acceptor for a ruthenium alkylidene derived from a 1,1-disubstituted olefin in a RCM process.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933168/catalytic-enantioselective-synthesis-of-polycyclic-nitrogen-oxygen-and-sulfur-heterocycles-via-rh-catalyzed-alkene-hydroacylation
#11
Kevin L Vickerman, Levi M Stanley
Enantioselective synthesis of polycyclic nitrogen, oxygen, and sulfur heterocycles by rhodium-catalyzed intramolecular alkene hydroacylation is reported. The intramolecular hydroacylation reactions generate 1,4-dihydrocyclopenta[b]indol-3(2H)-ones and 3,4-dihydrocyclopenta[b]indol-1(2H)-one in moderate-to-high yields (65-99%) with good-to-excellent enantioselectivities (84-99% ee). The catalyst system also promotes alkene hydroacylation of 3-vinylfuran-, 3-vinylbenzothiophene-, and 3-vinylthiophene-2-carboxaldehydes to generate the corresponding ketone products in moderate-to-high yields (71-91% yield) with excellent enantioselectivities (97-99% ee)...
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933167/tunable-cyclization-strategy-for-the-synthesis-of-zizaene-allo-cedrane-seco-kaurane-and-seco-atesane-type-skeletons
#12
Qianqian Yang, Wenjing Ma, Gaopeng Wang, Wenli Bao, Xiaoshu Dong, Xuefeng Liang, Lizhi Zhu, Chi-Sing Lee
A versatile Lewis acid-mediated cyclization strategy has been developed for selectively establishing zizaene-, allo-cedrane-, seco-kaurane-, and seco-atesane-type skeletons. The zizaene- and seco-atesane-type skeletons can be obtained in a cascade manner, which involves Diels-Alder reaction of cyclic enones with bis-silyloxy dienes and carbocyclization of yne-enolates through Lewis acid dependent 5- or 6-exo-dig modes. This cyclization strategy was also employed for the core synthesis of tashironin.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933166/direct-aziridination-of-nitroalkenes-affording-n-alkyl-c-nitroaziridines-and-the-subsequent-lewis-acid-mediated-isomerization-to-%C3%AE-nitroenamines
#13
Feiyue Hao, Haruyasu Asahara, Nagatoshi Nishiwaki
A mild and highly diastereoselective one-pot synthesis of trans-N-alkyl-C-nitroaziridines was achieved by treatment of nitroalkenes with aliphatic amines and N-chlorosuccinimide. Treatment of the obtained aziridines with a Lewis acid resulted in a facile ring opening reaction, accompanied by rearrangement and isomerization into functionalized (Z)-β-nitroenamines.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933165/ir-iii-catalyzed-direct-c-h-functionalization-of-arylphosphine-oxides-a-strategy-for-mop-type-ligands-synthesis
#14
Zhong Liu, Ji-Qiang Wu, Shang-Dong Yang
Diazo compounds as coupling partners are efficiently applied to Ir(III)-catalyzed direct C-H functionalization of arylphosphine oxides. Involving C-H activation, carbene insertion, and tautomerism, this reaction proceeds under mild conditions, thus proving an approach to the synthesis of MOP-type ligand precursor in a single step. The utility of this transformation has been further demonstrated in ligand synthesis as well as in the construction of phosphole framework.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933164/correction-to-synthesis-and-n-methyl-d-aspartate-nmda-receptor-activity-of-ketamine-metabolites
#15
Patrick J Morris, Ruin Moaddel, Panos Zanos, Curtis E Moore, Todd D Gould, Carlos A Zarate, Craig J Thomas
No abstract text is available yet for this article.
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933163/lissodendoric-acids-a-and-b-manzamine-related-alkaloids-from-the-far-eastern-sponge-lissodendoryx-florida
#16
Ekaterina G Lyakhova, Sophia A Kolesnikova, Anatoly I Kalinovsky, Dmitrii V Berdyshev, Evgeny A Pislyagin, Aleksandra S Kuzmich, Roman S Popov, Pavel S Dmitrenok, Tatyana N Makarieva, Valentin A Stonik
The first representatives of a new group of manzamine-related alkaloids with a previously unknown skeletal systems, namely, lissodendoric acids A (1) and B (2), were isolated from the sponge Lissodendoryx florida collected from the Sea of Okhotsk. The structures and absolute configurations have been elucidated by extensive spectroscopic analysis together with chemical transformations and quantum-chemical modeling. The lissodendoric acids show a potent capability to decrease the production of reactive oxygen species in neuroblastoma Neuro 2a and somewhat increase the survival of these cells upon treatment with 6-hydroxydopamine (an in vitro antiparkinson biotest)...
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28933145/synthesis-of-sulfanylated-difluoroalkenes-electrophilic-difluoromethylidenation-of-dithioesters-with-difluorocarbene
#17
Ryo Takayama, Atsushi Yamada, Kohei Fuchibe, Junji Ichikawa
Electrophilic difluoromethylidenation of dithioesters was achieved in high yields via the reaction with difluorocarbene. When aryl or alkyl dithiocarboxylates were treated with trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate in the presence of 5 mol % of a Proton Sponge catalyst, the in situ generated difluorocarbene reacted with the dithioesters to afford 2-sulfanylated 1,1-difluoro-1-alkenes via difluorothiiranes. This reaction can be considered as an electrophilic counterpart of the Wittig-type difluoromethylidenation of carbonyl compounds with nucleophilic difluoromethylene ylides...
September 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28930466/a-stereoselective-michael-mannich-annelation-strategy-for-the-construction-of-novel-tetrahydrocarbazoles
#18
David R Williams, Seth A Bawel, Richard N Schaugaard
A novel annelation strategy has been devised for stereoselective synthesis of tetrahydrocarbazoles. The pathway features a regio- and stereocontrolled condensation of indole and its substituted derivatives with electron-deficient 1,3-dienes via a Michael-Mannich reaction sequence. An extension of this method to include cross-conjugated allenes as substrates also results in a Michael-Mannich-Michael cascade, incorporating 2 equiv of indole with increasing product complexity. The formal 4π + 2π cyclization describes a concise route to polycyclic alkaloids of this family...
September 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28929770/pyridyl-directed-cp-rh-iii-catalyzed-b-3-h-acyloxylation-of-o-carborane
#19
Chun-Xiao Li, Hao-Yun Zhang, Tsz-Yung Wong, Hou-Ji Cao, Hong Yan, Chang-Sheng Lu
An efficient pyridyl-directed Rh(III)-catalyzed o-carborane B(3)-H acyloxylation is reported. The B(3)-H bond is the most electron-deficient vertex on o-carborane whose functionalization is challenging. The combination of Cu(OH)2 and diverse carboxylic acids provides low cost and abundant acyloxyl sources which could lead to moderate to excellent yields.
September 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28929767/sonogashira-reaction-using-arylsulfonium-salts-as-cross-coupling-partners
#20
Ze-Yu Tian, Shi-Meng Wang, Su-Jiao Jia, Hai-Xia Song, Cheng-Pan Zhang
Triarylsulfonium, alkyl- and fluoroalkyl(diaryl)sulfonium, and aryl(dialkyl)sulfonium triflates are successfully used as a new family of cross-coupling participants in the Sonogashira reaction as aryldiazonium, diaryliodonium, and tetraphenylphosphonium salts. It was found that terminal alkynes reacted mildly with triarylsulfonium or (2,2,2-trifluoroethyl)diphenylsulfonium triflate at room temperature under Pd- and Cu-cocatalysis to give the corresponding arylalkynes in up to >99% yield. This protocol represents the first use of arylsulfonium salts as cross-coupling partners in the Pd/Cu-catalyzed Sonogashira reaction...
September 20, 2017: Organic Letters
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