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Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry

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https://www.readbyqxmd.com/read/29904236/investigating-the-enantiodetermining-step-of-a-chiral-lewis-base-catalyzed-bromocycloetherification-of-privileged-alkenes
#1
Dietrich Böse, Scott E Denmark
The development of catalytic, enantioselective halofunctionalizations of unactivated alkenes has made significant progress in recent years. However, the identification of generally applicable catalysts for wide range of substrates has yet to be realized. A detailed understanding of the reaction mechanism is essential to guide the formulation of a truly general catalyst. Herein, we present our investigations on the enantiodetermining step of a Lewis base catalyzed bromocycloetherification that provides important insights and design criteria...
March 2018: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29910538/facile-synthesis-of-3-amido-dienynes-via-a-tandem-%C3%AE-propargylation-isomerization-of-chiral-allenamides-and-their-applications-in-diels-alder-cycloadditions
#2
Zhi-Xiong Ma, Li-Chao Fang, Richard P Hsung
A series of de novo 3-amido-dienynes was synthesized via tandem α-propargylation-isomerization of chiral allenamides with moderate E/Z ratio. Reactivities of E -and Z -isomers were examined.
December 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29904235/unexpected-rearrangement-of-2-bromoaniline-under-biphasic-alkylation-conditions
#3
Scott J Barraza, Scott E Denmark
Alkylation of 2-bromoaniline with benzyl bromide under ostensibly basic N-alkylation conditions resulted in migration of bromine from the 2- to the 4-aryl position. Herein we report our studies to elucidate the mechanism of this rearrangement with the objective of suppressing this unexpected outcome. We find that careful choice of reagents is critical, and that this behavior may be extrapolated to alkylation reactions of electron-rich bromo- and iodoanilines in general.
December 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29861552/a-photochemical-two-step-formal-5-2-cycloaddition-a-condensation-ring-expansion-approach-to-substituted-azepanes
#4
Scott M Thullen, David M Rubush, Tomislav Rovis
Seven-membered nitrogen-containing heterocycles are considerably underrepresented in the literature compared to their five- and six-membered analogues. Herein, we report a relatively understudied photochemical rearrangement of N-vinylpyrrolidinones to azepin-4-ones in good yields. This transformation allows for the conversion of readily available pyrrolidinones and aldehydes to densely functionalized azepane derivatives in a facile two step procedure.
December 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29904234/understanding-site-selectivity-in-the-palladium-catalyzed-cross-coupling-of-allenylsilanolates
#5
Scott E Denmark, Andrea Ambrosi
Allenylsilanolates can undergo cross-coupling at the α- or γ-terminus, and site selectivity appears to be determined by the intrinsic transmetalation mechanism. Fine-tuning of concentration, nucleophilicity, and steric bulk of the silanolate moiety allows for the selective formation of one isomer over the other. Whereas the α-isomer can be obtained in synthetically useful yield, the γ-isomer is favored only when employing reaction conditions that are inevitably associated with diminished reactivity.
November 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29033500/synthesis-of-3-3-disubstituted-indolenines-utilizing-the-lewis-acid-catalyzed-alkylation-of-2-3-disubstituted-indoles-with-trichloroacetimidates
#6
Arijit A Adhikari, Léa Radal, John D Chisholm
Trichloroacetimidates function as effective electrophiles for the selective C3-alkylation of 2,3-disubstituted indoles to provide 3,3'-disubstituted indolenines. These indolenines are common synthetic intermediates that are often utilized in the synthesis of complex molecules. Effective reaction conditions utilizing Lewis acid catalysts have been determined, and the scope of the reaction with respect to indole and imidate reaction partner has been investigated. This chemistry provides an alternative to base promoted and transition metal catalyzed methods that are more commonly utilized to access similar indolenines...
October 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29904233/unnatural-amino-acid-derivatives-through-click-chemistry-synthesis-of-triazolylalanine-analogues
#7
Pravin C Patil, Frederick A Luzzio
A novel tert -butyl 2-(1-oxoisolndolin-2-yl)acetate derivative is selectively alkylated with propargyl bromide in the presence of lithium hexamethyldisilazide. After removal of the tert -butyl protecting group, the resulting N -isoindolinyl (ethynylalanine) derivative is reacted with a series of azides under 'click conditions'. The click reactions afford an array of N -isoindolinyl-1,2,3-triazolylalanine derivatives as the free carboxylic adds. Following esterification, the N -isoindolinone protecting group is then transformed into the more easily removable phthaloyl group by selective oxidation at the benzylic position...
September 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/28993718/substituent-effects-on-carbon-acidity-in-aqueous-solution-and-at-enzyme-active-sites
#8
Tina L Amyes, John P Richard
Methods are described for the determination of pKas for weak carbon acids in water. The application of these methods to the determination of the pKas for a variety of carbon acids including nitriles, imidazolium cations, amino acids, peptides and their derivatives and, α-iminium cations is presented. The substituent effects on the acidity of these different classes of carbon acids are discussed; and, the relevance of these results to catalysis of the deprotonation of amino acids by enzymes and by pyridoxal 5'-phosphate is reviewed...
July 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/28413263/intensified-microwave-assisted-n-acylation-procedure-synthesis-and-activity-evaluation-of-trpc3-channel-agonists-with-a-1-3-dihydro-2h-benzo-d-imidazol-2-one-core
#9
Gema Guedes de la Cruz, Barbora Svobodova, Michaela Lichtenegger, Oleksandra Tiapko, Klaus Groschner, Toma Glasnov
Upon controlled microwave heating and using cyanuric chloride as a coupling reagent, an efficient amidation procedure for the synthesis of 1,3-dihydro-2H-benzo[d]imidazol-2-one-based agonists of TRPC3/6 ion channels has been developed. Compared to the few conventional protocols, a drastic reduction in processing time from ca. 2 days down to 10 minutes was achieved accompanied by significantly improved product yields. The robustness of the method was confirmed by 18 additional examples including aromatic, aliphatic, and heterocyclic amines and acids...
April 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/28713205/khf-2-a-mild-and-selective-desilylating-agent-for-phenol-t-butyldimethylsilyl-tbdms-ethers
#10
Mahesh K Lakshman, Fatou A Tine, Tashrique A Khandaker, Vikram Basava, Nana B Agyemang, Michael S A Benavidez, Marikone Gaši, Lisa Guerrera, Barbara Zajc
TBDMS ( t -BuMe2 Si, t -butyldimethylsilyl) ethers of a variety of phenols have been deprotected with KHF2 in MeOH, at room temperature. Carboxylic ester and labile phenolic acetate were unaffected under these conditions. In competition reactions between TBDMS ethers of a phenol and two primary benzylic alcohols, the phenolic ether underwent cleavage whereas the alcohol ethers remained intact. From a substrate containing both a phenolic hydroxyl group and a secondary, doubly benzylic hydroxyl group protected as TBDMS ethers, the phenol was rapidly and selectively released...
March 2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29540961/pardon-the-interruption-a-modification-of-fischer-s-venerable-reaction-for-the-synthesis-of-heterocycles-and-natural-products
#11
Robert B Susick, Lucas A Morrill, Elias Picazo, Neil K Garg
This account provides an overview of our laboratory's studies of an unusual variant of the Fischer indolization reaction. We describe the discovery of the so-called 'interrupted Fischer indolization' and the development of the reaction from a methodological standpoint. In addition, our efforts to evaluate and apply this methodology in the context of akuammiline alkaloid total synthesis are discussed.
2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29430080/high-yielding-automated-convergent-synthesis-of-no-carrier-added-11-c-carbonyl-labeled-amino-acids-using-the-strecker-reaction
#12
Junhao Xing, Allen F Brooks, Dylan Fink, Huibin Zhang, Morand R Piert, Peter J H Scott, Xia Shao
A new variant of the Strecker synthesis using no-carrier-added [11 C]cyanide for the synthesis of radiolabeled amino acids is described. The protocol is fully automated using a radiochemistry synthesis module and applied to the production of a number of new PET radiotracers. [11 C- Carbonyl ]sarcosine, [11 C- carbonyl ]methionine, [11 C- carbonyl ]- N -phenylglycine, and [11 C- carbonyl ]glycine are all synthesized in moderate to good radiochemical yields. The synthesis of [11 C- carbonyl ]sarcosine has been validated for production of doses for clinical use, and preliminary evaluation of the new radiotracer in PC3 tumor-bearing mice is also reported...
2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29398786/a-merged-aldol-condensation-alkene-isomerization-cycloaddition-cycloreversion-sequence-employing-oxazinone-intermediates-for-the-synthesis-of-substituted-pyridines
#13
Jill B Williamson, Emily R Smith, Jonathan R Scheerer
A domino reaction sequence has been evaluated that begins with union of novel dihydrooxazinone precursors with 2-alkynyl-substituted benzaldehyde components through aldol condensation. Ensuing operations, including alkene isomerization, Diels-Alder, and retrograde Diels-Alder with loss of CO2 occurs in the same reaction vessel to provide polysubstituted tricyclic pyridine products.
2017: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/28260839/metal-catalyzed-decarboxylative-fluoroalkylation-reactions
#14
Brett R Ambler, Ming-Hsiu Yang, Ryan A Altman
Metal-catalyzed decarboxylative fluoroalkylation reactions enable the conversion of simple O-based substrates into biologically relevant fluorinated analogs. Herein, we present decarboxylative methods that facilitate the synthesis of trifluoromethyl- and difluoroketone-containing products. We highlight key mechanistic aspects that are critical for efficient catalysis, and that inspired our thinking while developing the reactions.
December 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/27766017/benzylic-ammonium-ylide-mediated-epoxidations
#15
Lukas Roiser, Raphaël Robiette, Mario Waser
A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out.
August 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/27493448/aqueous-lanthanide-chemistry-in-asymmetric-catalysis-and-magnetic-resonance-imaging
#16
Matthew J Allen
This account describes lanthanide coordination chemistry with a focus on the similarities between lanthanide complexes used in catalysis and those used as contrast agents in magnetic resonance imaging.
June 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/27065567/facile-and-high-yielding-synthesis-of-tam-biradicals-and-monofunctional-tam-radicals
#17
Dmitry V Trukhin, Olga Yu Rogozhnikova, Tatiana I Troitskaya, Vladimir G Vasiliev, Michael K Bowman, Victor M Tormyshev
Facile and high-yielding procedures for synthesis of monocarboxylic acid derivatives of triarylmethyl radicals (TAMs) were developed. Reaction of methyl thioglycolate with tris(2,3,5,6-tetrathiaaryl)methyl cation smoothly afforded the monosubstituted TAM derivative, which was hydrolyzed to a monocarboxylic acid, with the TAM moiety attached to thioglycolic acid via the sulfur atom. Alternatively, the diamagnetic tricarboxylic acid precursor of Finland trityl was transformed to a trimethyl ester and partially hydrolyzed under controlled conditions...
April 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/29276340/highly-stereoselective-intermolecular-haloetherification-and-haloesterification-of-allyl-amides
#18
B Soltanzadeh, A Jaganathan, B Borhan
No abstract text is available yet for this article.
February 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/27872511/synthesis-of-trifluoromethoxylated-hetero-arenes-via-ocf3-migration
#19
Katarzyna N Lee, Johnny W Lee, Ming-Yu Ngai
Incorporation of the OCF3 group into organic molecules, especially aromatic and heteroaromatic compounds, is recognized as one of the major challenges in synthetic organic chemistry. Although many attempts have been made to develop efficient trifluoromethoxylation strategies, most of the current approaches still require use of highly toxic, thermally unstable reagents, or impractical reaction conditions. Herein, we highlight a recent contribution from our group towards the synthesis of (hetero)aryltrifluoromethyl ethers...
February 2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
https://www.readbyqxmd.com/read/27397970/synthesis-of-amino-adt-provides-access-to-hydrolytically-stable-amide-coupled-hydrogen-sulfide-releasing-drug-targets
#20
Matthew D Hammers, Loveprit Singh, Leticia A Montoya, Alan D Moghaddam, Michael D Pluth
As additional physiological functions of hydrogen sulfide (H2S) are discovered, developing practical methods for exogenous H2S delivery is important. In particular, nonsteroidal anti-inflammatory drugs (NSAIDs) functionalized with H2S-releasing anethole dithiolethione (ADT-OH) through ester bonds are being investigated for their combined anti-inflammatory and antioxidant potential. The chemical robustness of the connection between drug and H2S-delivery components, however, is a key and controllable linkage in these compounds...
2016: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry
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