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Chun-Tian Li, Hui Liu, Yan-Jun Xu, Chong-Dao Lu
Diastereoselective aldol reaction of N-tert-butanesulfinyl imidates under typical hard enolization conditions is reported. Potassium bis(trimethylsilyl)amide (KHMDS) effectively promotes the aldol reaction of α-aryl- and α-alkyl-substituted imidates, providing anti-aldol adducts in high yields with good to excellent diastereoselectivities. In the case of α-aryl imidates, high conversion depends on adding trimethylsilyl chloride (TMSCl) to the reaction mixture. In the presence of a suitable Lewis acid, cyclohexanone is a good electrophile in the aldol reaction of imidates...
September 19, 2017: Journal of Organic Chemistry
Andreas Boelke, Lucien D Caspers, Boris J Nachtsheim
The first directing-group-mediated C-H alkenylation with alkenyl-λ(3)-iodanes as electrophilic alkene-transfer reagents has been developed. The application of free aromatic amines as challenging but synthetically valuable directing groups in combination with an Ir(III) catalyst enabled the synthesis of highly desirable 1,3-dienes in excellent yields of up to 98% with high to perfect (Z,E) stereoselectivity. A broad substrate scope and further synthetic modifications are demonstrated.
September 19, 2017: Organic Letters
Yong Guan, Steven D Townsend
A one-pot, metal-free procedure has been developed to synthesize unsymmetrical organoselenides. In the first step of the reaction, arylation of potassium selenocyanate (KSeCN) with an iodonium reagent proceeds in the absence of a metal catalyst to produce an arylselenocyanate. In the second step, treatment with sodium borohydride unmasks a second selenium nucleophile that engages an aliphatic electrophile, iodonium reagent, or glycosyl halide. The procedure represents an umpolung approach to the synthesis of aryl-selenides...
September 19, 2017: Organic Letters
Hiroaki Iwamoto, Yu Ozawa, Koji Kubota, Hajime Ito
The copper(I)-catalyzed regio- and stereoselective intramolecular alkylation of propargyl ethers and amines bearing an alkyl electrophilic moiety has been developed. The reaction showed high functional group tolerance and gave highly functionalized alkenylboronates bearing heterocyclic rings, which are versatile synthetic intermediates in organic chemistry. The borylation products can be transformed into multi-substituted alkenes through stereospecific transformations. Mechanistic studies showed that the chemo- and stereoselectivity of copper(I)-catalyzed borylation depends on the type of leaving group...
September 19, 2017: Journal of Organic Chemistry
Sven Tobisch
This first comprehensive computational study of the copper-mediated formal aminoboration utilising an electrophilic strategy has identified the most accessible pathway for the productive catalysis. The mechanistic picture derived from smooth energy profiles acquired by employing a reliable computational protocol applied to a realistic catalyst model conforms to all available experimental data. The high degree of chemo- and stereoselectivity achieved in syn-borylcupration and Umpolung electrophilic amination is instrumental to the exclusive generation of the (syn)-beta-aminoalkylborane product...
September 19, 2017: Chemistry: a European Journal
Waqar Rauf, John M Brown
Silyl-substituted aromatic compounds can participate as the electrophilic component in palladium-catalysed cross-couplings, and reactivity is enhanced by a neighbouring silyl-group. Products analogous to those obtained from C-H activation chemistry are accessible by this means with the additional benefit of regiochemistry defined by the site of silyl substitution. DFT studies described here show that the mechanism of C-Si cleavage is distinct from previously recognised mechanisms for C-H cleavage, with a cascade of silyl intermediates en route to a stable product...
September 19, 2017: Organic & Biomolecular Chemistry
Xiaofeng Ma, Joshua Farndon, Tom Young, Natalie Fey, John Bower
A C-N bond forming dearomatization protocol with broad scope is outlined. Specifically, bifunctional amino-reagents are used for sequential nucleophilic and electrophilic C-N bond formations, with the latter effecting the key dearomatization step. Using this approach, γ-arylated alcohols are converted to a wide range of differentially protected spirocyclic pyrrolidines in just two or three steps.
September 19, 2017: Angewandte Chemie
Abdallah Zeineddine, Laura Estévez, Sonia Mallet-Ladeira, Karinne Miqueu, Abderrahmane Amgoune, Didier Bourissou
The reluctance of gold to achieve oxidative addition reaction is considered as an intrinsic limitation for the development of gold-catalyzed cross-coupling reactions with simple and ubiquitous aryl halide electrophiles. Here, we report the rational construction of a Au(I)/Au(III) catalytic cycle involving a sequence of Csp(2)-X oxidative addition, Csp(2)-H auration and reductive elimination, allowing a gold-catalyzed direct arylation of arenes with aryl halides. Key to this discovery is the use of Me-Dalphos, a simple ancillary (P,N) ligand, that allows the bottleneck oxidative addition of aryl iodides and bromides to readily proceed under mild conditions...
September 18, 2017: Nature Communications
Dominik S Allgäuer, Harish Jangra, Haruyasu Asahara, Zhen Li, Quan Chen, Hendrik Zipse, Armin R Ofial, Herbert Mayr
In order to quantify the electrophilic reactivities of common Michael acceptors, we measured the kinetics of the reactions of monoacceptor-substituted ethylenes (H2C═CH-Acc, 1) and styrenes (PhCH═CH-Acc, 2) with pyridinium ylides 3, sulfonium ylide 4, and sulfonyl-substituted chloromethyl anion 5. Substitution of the 57 measured second-order rate constants (log k) and the previously reported nucleophile-specific parameters N and sN for 3-5 into the correlation log k = sN(E + N) allowed us to calculate 15 new empirical electrophilicity parameters E for Michael acceptors 1 and 2...
September 18, 2017: Journal of the American Chemical Society
Alessandra Scala, Rossana Mirabella, Joachim Goedhart, Michel de Vries, Michel A Haring, Robert C Schuurink
This work adds a new player, HER2, downstream of the perception of E-2-hexenal, a green leaf volatile, and shows that E-2-hexenal specifically changes the redox status of the mitochondria. It is widely accepted that plants produce and respond to green leaf volatiles (GLVs), but the molecular components involved in transducing their perception are largely unknown. The GLV E-2-hexenal inhibits root elongation in seedlings and, using this phenotype, we isolated E-2-hexenal response (her) Arabidopsis thaliana mutants...
September 16, 2017: Plant Molecular Biology
Tomonori Tamura, Zhining Song, Kazuma Amaike, Shin Lee, Sifei Yin, Shigeki Kiyonaka, Itaru Hamachi
Catalyst-mediated protein modification is a powerful approach for the imaging and engineering of natural proteins. We have previously developed affinity-guided 4-dimethylaminopyridine (DMAP) (AGD) chemistry as an efficient protein modification method using a catalytic acyl transfer reaction. However, because of the high electrophilicity of the thioester acyl donor molecule, AGD chemistry suffers from nonspecific reactions to proteins other than the target protein in crude biological environments, such as cell lysates, live cells, and tissue samples...
September 15, 2017: Journal of the American Chemical Society
Masaharu Sugiura, Takeru Kashiwagi, Mai Ito, Shunsuke Kotani, Makoto Nakajima
The domino reaction of enamines, electrophiles (N-sulfonylimines, N-tosylisocyanate, or diethyl azodicarboxylate), and trichlorosilane provided trans-amines (trans/cis = >99:1 to 96:4). Meanwhile, the sequential imino ene-type reaction of enamines and electrophiles/NaBH3CN reduction afforded cis-amines (trans/cis = 1:>99 to 15:85). The reversal of selectivity is discussed on the basis of diastereofacial selection of the plausible iminium ion intermediates. For the domino reaction of cyclic enamines and cyclic imines, high enantioselectivity (er = 95...
September 15, 2017: Journal of Organic Chemistry
You Yang, Biao Yu
Advances in the chemical synthesis of C-pyranosides/furanosides are summarized, covering the literature from 2000 to 2016. The majority of the methods take advantage of the construction of the glycosidic C-C bond. These C-glycosylation methods are categorized herein in terms of the glycosyl donor precursors, which are commonly used in O-glycoside synthesis and are easily accessible to nonspecialists. They include glycosyl halides, glycals, sugar acetates, sugar lactols, sugar lactones, 1,2-anhydro sugars, thioglycosides/sulfoxides/sulfones, selenoglycosides/telluroglycosides, methyl glycosides, and glycosyl imidates/phosphates...
September 15, 2017: Chemical Reviews
Zhichen Lin, Zhongyan Hu, Xin Zhang, Jinhuan Dong, Jian-Biao Liu, De-Zhan Chen, Xianxiu Xu
A tandem [3 + 2] cycloaddition/reductive cyclization of nitrochalcones with activated methylene isocyanides for the efficient synthesis of pyrrolo[2,3-b]quinolones is reported. In this reaction, the in situ generated dihydropyrroline acts as the internal reductant to convert the nitro into an electrophilic nitroso group, which undergoes subsequent C-N bond formation. Transition-metal-free, simple experimental procedure and ready accessibility of starting materials characterize the present transformation.
September 14, 2017: Organic Letters
Christopher D McCune, Matthew L Beio, Jill M Sturdivant, Roberto de la Salud-Bea, Brendan M Darnell, David B Berkowitz
Developing specific chemical functionalities to deploy in biological environments for targeted enzyme inactivation lies at the heart of mechanism-based inhibitor (MBI) development, but also is central to other protein-tagging methods in modern chemical biology including activity-based protein profiling (ABPP) and proteolysis-targeting chimeras (PROTACS). We describe here a previously unknown class of potential PLP enzyme inactivators; namely, a family of quaternary, α-(1'fluoro)vinyl amino acids, bearing the side chains of the cognate amino acids...
September 14, 2017: Journal of the American Chemical Society
Benedikt C Melzer, Franz Bracher
Oxoisoaporphine alkaloids are conveniently prepared via direct ring metalation of alkoxy-substituted isoquinolines at C-1, followed by reaction with iodine. Subsequent Suzuki cross-coupling of the resulting 1-iodoisoquinolines to methyl 2-(isoquinolin-1-yl)benzoates and intramolecular acylation of the corresponding carboxylic acids with Eaton's reagent afforded five alkaloids of the oxoisoaporphine type. The yield of the cyclization step strongly depends on the electrophilic properties of ring B. An alternative cyclization protocol via directed remote metalation of ester and amide intermediates was investigated thoroughly, but found to be not feasible...
2017: Beilstein Journal of Organic Chemistry
M Kavimani, V Balachandran, B Narayana, K Vanasundari, B Revathi
Experimental FT-IR and FT-Raman spectra of 2-methylphenylacetic acid (MPA) were recorded and theoretical values are also analyzed. The non-linear optical (NLO) properties were evaluated by determination of first (5.5053×10(-30) e.s.u.) and second hyper-polarizabilities (7.6833×10(-36) e.s.u.) of the title compound. The Multiwfn package is used to find the weak non-covalent interaction (Van der Wall interaction) and strong repulsion (steric effect) of the molecule and examined by reduced density gradient. The molecular electrostatic potential (MEP) analysis used to find the most reactive sites for the electrophilic and nucleophilic attack...
September 7, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jennifer R Griffin, Chloe I Wendell, Jacob A Garwin, M Christina White
The catalytic transformation of a C(sp3)-H bond to a C(sp3)-C bond via an iron carbene intermediate represents a long-standing challenge. Despite the success of enzymatic and small molecule iron catalysts mediating challenging C(sp3)-H oxidations and aminations via high-valent iron oxos and nitrenes, C(sp3)-H alkylations via isoelectronic iron carbene intermediates have thus far been unsuccessful. Iron carbenes have been inert, or shown to favor olefin cyclopropanation and heteroatom-hydrogen insertion. Herein we report an iron phthalocyanine-catalyzed alkylation of allylic and benzylic C(sp3)-H bonds...
September 12, 2017: Journal of the American Chemical Society
Jiandong Wang, Shichong Jia, Kenta Okuyama, Zhongyan Huang, Etsuko Tokunaga, Yuji Sumii, Norio Shibata
A novel pentafluorobenzenesulfonyl hypervalent iodonium ylide 3 was designed and synthesized as a useful tool for the preparation of sulfur pentafluorophenyl compounds containing a C6F5S or C6F5SO2 unit. Electrophilic pentafluorophenylthiolation of enamines, formal [3+2] cycloaddition reaction of nitriles and alkynes, and intramolecular SNAr cyclization were achieved using iodonium ylide 3. The fluorine-click reaction was also demonstrated using one of the products via an intermolecular SNAr reaction with hetero-centered nucleophiles...
September 12, 2017: Journal of Organic Chemistry
Giovanna Parisi, Marco Colella, Serena Monticelli, Giuseppe Romanazzi, Wolfgang Holzer, Thierry Langer, Leonardo Degennaro, Vittorio Pace, Renzo Luisi
The first direct and straightforward nucleophilic fluoromethylation of organic compounds is reported. The tactic employs a "fleeting" lithium fluorocarbenoid (LiCH2F) generated from commercially available fluoroiodomethane. Precise reaction conditions were devel-oped for generation and synthetic exploitation of such a labile spe-cies. The versatility of the strategy is showcased in about 50 examples involving a plethora of electrophiles. Highly valuable chemicals such as fluoro alcohols, fluoro amines and fluoromethylated oxy-genated heterocycles could be prepared in very good yields through a single synthetic operation...
September 11, 2017: Journal of the American Chemical Society
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