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https://www.readbyqxmd.com/read/28510320/selective-si-c-sp3-bond-cleavage-in-aminomethyl-silanes-by-carbanionic-nucleophiles-and-its-stereochemical-course
#1
Stephan G Koller, Jonathan O Bauer, Carsten Strohmann
The utilization of tetraorganosilanes by selective cleavage of a silicon-carbon bond is still a great challenge. Here we describe a new type of Si-C(sp3) bond cleavage in bench-stable (aminomethyl)silanes with common organolithium reagents as nucleophiles. Suitable leaving groups are benzyl, allyl, and phenylthiomethyl groups. A β-donor function and polar solvents are essential. Through slight modifications of the reaction conditions, easy switching between α-deprotonation and substitution is possible. Using a silicon-chiral benzylsilan, the stereochemical course of the reaction was elucidated...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28503205/substitution-of-fluorine-in-m-c6f5bf3-with-organolithium-compounds-distinctions-between-o-and-n-nucleophiles
#2
Anton Yu Shabalin, Nicolay Yu Adonin, Vadim V Bardin
Borates M[C6F5BF3] (M = K, Li, Bu4N) react with organolithium compounds, RLi (R = Me, Bu, Ph), in 1,2-dimethoxyethane or diglyme to give M[4-RC6F4BF3] and M[2-RC6F4BF3]. When R is Me or Bu, the nucleophilic substitution of the fluorine atom at the para position to boron is the predominant route. When R = Ph, the ratio M[4-RC6F4BF3]/M[2-RC6F4BF3] is ca. 1:1. Substitution of the fluorine atom at the ortho position to boron is solely caused by the coordination of RLi via the lithium atom with the fluorine atoms of the BF3 group...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28497884/practical-method-for-the-catalytic-enantioselective-arylation-and-heteroarylation-of-ketones-with-organotitanium-reagents-generated-in-situ-from-bromide-and-heteroarene-precursors
#3
Atsushi Matsuda, Tomoya Ushimaru, Yusuke Kobayashi, Toshiro Harada
A practically useful, catalytic enantioselective method has been developed for the synthesis of tertiary diaryl and aryl heteroaryl carbinols starting from commercially available aromatic ketones and aryl or heteroaryl bromides. In this method, organotitanium reagents are generated in situ from the bromides by lithiation with BuLi followed by transmetallation of the resulting organolithiums with ClTi(OiPr)3. Treatment of the ketones with the titanium reagents in the presence of (R)-3-(3,5-bistrifluoromehthylphenyl)-1,1'-bi-2-naphthol (BTFP-BINOL) affords the corresponding tertiary alcohols in high enantioselectivities and yields...
May 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28453280/synthesis-of-functionalized-alkenes-by-a-transition-metal-free-zweifel-coupling
#4
Roly J Armstrong, Worawat Niwetmarin, Varinder K Aggarwal
The Zweifel reaction is a powerful method for the synthesis of alkenes, serving as a transition-metal-free alternative to the Suzuki-Miyaura reaction. To date, the scope of the Zweifel coupling has been rather narrow and has focused mainly on the coupling of vinyllithium reagents to synthesize simple aryl- and alkyl-substituted olefins. Herein, the development of a general transition-metal-free coupling process enabling the coupling of Grignard reagents or organolithiums is described. This method enables the enantiospecific synthesis of a wide variety of functionalized acyclic and cyclic olefin products...
April 28, 2017: Organic Letters
https://www.readbyqxmd.com/read/28422251/-anti-michael-addition-of-grignard-reagents-to-sulfonylacetylenes-synthesis-of-alkynes
#5
Francisco Esteban, Lazhar Boughani, José L García Ruano, Alberto Fraile, José Alemán
In this work, the addition of Grignard reagents to arylsulfonylacetylenes, which undergoes an "anti-Michael addition", resulting in their alkynylation under very mild conditions is described. The simplicity of the experimental procedure and the functional group tolerance are the main features of this methodology. This is an important advantage over the use of organolithium at -78 °C that we previously reported. Moreover, the synthesis of diynes and other examples showing functional group tolerance in this anti-Michael reaction is also presented...
May 10, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28368117/lithium-diisopropylamide-nonequilibrium-kinetics-and-lessons-learned-about-rate-limitation
#6
Russell F Algera, Lekha Gupta, Alexander C Hoepker, Jun Liang, Yun Ma, Kanwal J Singh, David B Collum
The kinetics of lithium diisopropylamide (LDA) in tetrahydrofuran under nonequilibrium conditions are reviewed. These conditions correspond to a class of substrates in which the rates of LDA aggregation and solvation events are comparable to the rates at which various fleeting intermediates react with substrate. Substrates displaying these reactivities, by coincidence, happen to be those that react at tractable rates on laboratory time scales at -78 °C. In this strange region of nonlimiting behavior, rate-limiting steps are often poorly defined, sometimes involve deaggregation, and at other times include reaction with substrate...
May 5, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28295938/alkenyl-isocyanide-conjugate-additions-a-rapid-route-to-%C3%AE-carbolines
#7
Sergiy V Chepyshev, J Armando Lujan-Montelongo, Allen Chao, Fraser F Fleming
Isocyanides are exceptional building blocks, the wide deployment of which in multicomponent and metal-insertion reactions belies their limited availability. The first conjugate addition/alkylation to alkenyl isocyanides is described, which addresses this deficiency. An array of organolithiums, magnesiates, enolates, and metalated nitriles add conjugately to β- and β,β-disubstituted arylsulfonyl alkenyl isocyanides to rapidly assemble diverse isocyanide scaffolds. The intermediate metalated isocyanides are efficiently trapped with electrophiles to generate substituted isocyanides incorporating contiguous tri- and tetra-substituted centers...
April 3, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28235381/stereoselective-arylation-of-amino-aldehydes-overriding-natural-substrate-control-through-chelation
#8
Bruna S Martins, Angélica V Moro, Diogo S Lüdtke
The chelation-controlled arylation reaction of chiral, enantiopure acyclic α-amino aldehydes enabled by a B/Zn exchange reaction between arylboronic acids and Et2Zn is reported. The presence of dibenzyl substituents at the nitrogen plays a key role in the stereochemical outcome of the reaction, and chelation is favored over the natural tendency of this type of substrate to undergo Felkin-Anh controlled additions with organomagnesium and organolithium reagents.
March 3, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230375/three-component-coupling-of-triflyloxy-substituted-benzocyclobutenones-organolithium-reagents-and-arynophiles-promoted-by-generation-of-aryne-via-carbon-carbon-bond-cleavage
#9
Keisuke Uchida, Suguru Yoshida, Takamitsu Hosoya
Treatment of benzocyclobutenones bearing a triflyloxy group adjacent to the four-membered ring with organolithium reagents in the presence of arynophiles efficiently affords three-component coupled α-arylketones. Mechanistic studies indicate that the reaction is promoted by generation of the aryne via carbon-carbon bond cleavage of a benzocyclobutenoxide intermediate, which led us to find a fluoride-mediated aryne generation method from triflyloxy-substituted benzocyclobutenone silyl acetal precursors.
February 23, 2017: Organic Letters
https://www.readbyqxmd.com/read/28194863/oxygen-activated-palladium-nanoparticle-catalyzed-ultrafast-cross-coupling-of-organolithium-reagents
#10
Dorus Heijnen, Filippo Tosi, Carlos Vila, Marc C A Stuart, Philip H Elsinga, Wiktor Szymanski, Ben L Feringa
The discovery of an ultrafast cross-coupling of alkyl- and aryllithium reagents with a range of aryl bromides is presented. The essential role of molecular oxygen to form the active palladium catalyst was established; palladium nanoparticles that are highly active in cross-coupling reactions with reaction times ranging from 5 s to 5 min are thus generated in situ. High selectivities were observed for a range of heterocycles and functional groups as well as for an expanded scope of organolithium reagents...
March 13, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28151465/cu-catalyzed-enantioselective-allylic-alkylation-with-organolithium-reagents
#11
Valentín Hornillos, Sureshbabu Guduguntla, Martín Fañanás-Mastral, Manuel Pérez, Pieter H Bos, Alena Rudolph, Syuzanna R Harutyunyan, Ben L Feringa
This protocol describes a method for the catalytic enantioselective synthesis of tertiary and quaternary carbon stereogenic centers, which are widely present in pharmaceutical and natural products. The method is based on the direct reaction between organolithium compounds, which are cheap, readily available and broadly used in chemical synthesis, and allylic electrophiles, using chiral copper catalysts. The methodology involves the asymmetric allylic alkylation (AAA) of allyl bromides, chlorides and ethers with organolithium compounds using catalyst systems based on Cu-Taniaphos and Cu-phosphoramidites...
March 2017: Nature Protocols
https://www.readbyqxmd.com/read/28111913/catalytic-double-carbon-boron-bond-formation-for-the-synthesis-of-cyclic-diarylborinic-acids-as-versatile-building-blocks-for-%C3%AF-extended-heteroarenes
#12
Takuya Igarashi, Mamoru Tobisu, Naoto Chatani
The first catalytic synthesis of cyclic diarylborinic acids is developed using a dihydroaminoborane reagent as the boron source. Unlike previously reported methods that use organolithium reagents, this method allows the easy synthesis of cyclic diarylborinic acids bearing a range of functionalities including CN, CO2 Et, CONEt2 and NMeCO2(t) Bu. Furthermore, these cyclic diarylborinic acids provide rapid access to skeletal diversity, in particular they enable the synthesis of six- to nine-membered π-extended heteroarenes through simple cross-coupling reactions, which are important synthetic targets in both advanced materials and pharmaceuticals...
January 23, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28099031/stereospecific-intramolecular-arylation-of-2-and-3-pyridyl-substituted-alkylamines-via-configurationally-stable-%C3%AE-pyridyl-organolithiums
#13
Julien Maury, Wojciech Zawodny, Jonathan Clayden
Treatment of N'-aryl urea derivatives of enantiomerically enriched α-(2-pyridyl) and α-(3-pyridyl)alkylamines with a base leads to the migration of the N'-aryl substituent from N to C in a 'nonclassical' intramolecular nucleophilic aromatic substitution reaction. Both electron-rich and -poor rings migrate successfully. A new quaternary stereogenic center is formed adjacent to the pyridine ring with high stereospecificity, even when the intermediate anion is a presumably planar 2-picolyllithium. Base hydrolysis of the urea gives enantiomerically enriched α-pyridylalkylamines...
January 18, 2017: Organic Letters
https://www.readbyqxmd.com/read/27978636/formation-of-seven-membered-carbocycles-via-7-endo-mode-cyclization-of-lithioheptatrienes
#14
Ken-Ichiro Kanno, Eri Igarashi, Yuki Mizukami, Kiyohiko Nakajima, Zhiyi Song, Tamotsu Takahashi
The highly selective synthesis of triene derivatives was achieved by a zirconocene-mediated three-component coupling reaction, and the trienes were efficiently subjected to 7-endo mode cyclization. The reaction of unsymmetrical zirconacyclopentadienes prepared from two different alkynes with N-bromosuccinimide (NBS) followed by treatment with allyl halides in the presence of CuCl afforded the corresponding heptatrienes in good yields. When the trienes reacted with an organolithium reagent, 7-endo mode cyclization occurred smoothly to give the corresponding cycloheptadiene...
December 16, 2016: Organic Letters
https://www.readbyqxmd.com/read/27911386/a-protocol-for-safe-lithiation-reactions-using-organolithium-reagents
#15
Michael R Gau, Michael J Zdilla
Organolithium reagents are powerful tools in the synthetic chemist's toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented...
November 12, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27891818/exploiting-deep-eutectic-solvents-and-organolithium-reagent-partnerships-chemoselective-ultrafast-addition-to-imines-and-quinolines-under-aerobic-ambient-temperature-conditions
#16
Cristian Vidal, Joaquín García-Álvarez, Alberto Hernán-Gómez, Alan R Kennedy, Eva Hevia
Shattering the long-held dogma that organolithium chemistry needs to be performed under inert atmospheres in toxic organic solvents, chemoselective addition of organolithium reagents to non-activated imines and quinolines has been accomplished in green, biorenewable deep eutectic solvents (DESs) at room temperature and in the presence of air, establishing a novel and sustainable access to amines. Improving on existing methods, this approach proceeds in the absence of additives; occurs without competitive enolization, reduction or coupling processes; and reactions were completed in seconds...
December 23, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27860115/jos%C3%A3-barluenga-1940-2016
#17
José M González, Kilian Muñiz
José Barluenga, emeritus professor at the University of Oviedo, passed away on September 7, 2016. Barluenga was one of the leading Spanish chemists of his generation, with research interests including metal-mediated activation of alkenes and alkynes, β-functionalized organolithium compounds, iodination reactions, asymmetric Diels-Alder reactions, carbene complexes, and cross-coupling reactions.
November 11, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27775313/a-new-2h-2h-1t-cophase-in-polycrystalline-mos2-and-mose2-thin-films
#18
Mehwish Naz, Toby Hallam, Nina C Berner, Niall McEvoy, Riley Gatensby, John B McManus, Zareen Akhter, Georg S Duesberg
We report on 2H-2H'/1T phase conversion of MoS2 and MoSe2 polycrystalline films grown by thermally assisted conversion. The structural conversion of the transition metal dichalcogenides was successfully carried out by organolithium treatment on chip. As a result we obtained a new 2H-2H'/1T cophase system of the TMDs thin films which was verified by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The conversion was successfully carried out on selected areas yielding a lateral heterostructure between the pristine 2H phase and the 2H'/1T cophase regions...
November 16, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27629250/cross-coupling-of-organolithium-with-ethers-or-aryl-ammonium-salts-by-c-o-or-c-n-bond-cleavage
#19
Ze-Kun Yang, Dong-Yu Wang, Hiroki Minami, Hiroyuki Ogawa, Takashi Ozaki, Tatsuo Saito, Kazunori Miyamoto, Chao Wang, Masanobu Uchiyama
Various aryl-, alkenyl-, and/or alkyllithium species reacted smoothly with aryl and/or benzyl ethers with cleavage of the inert C-O bond to afford cross-coupled products, catalyzed by commercially available [Ni(cod)2 ] (cod=1,5-cyclooctadiene) catalysts with N-heterocyclic carbene (NHC) ligands. Furthermore, the coupling reaction between the aryllithium compounds and aryl ammonium salts proceeded under mild conditions with C-N bond cleavage in the presence of a [Pd(PPh3 )2 Cl2 ] catalyst. These methods enable selective sequential functionalizations of arenes having both C-N and C-O bonds in one pot...
September 15, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27592551/exploring-the-reactivity-of-%C3%AE-lithiated-aryl-benzyl-ethers-inhibition-of-the-1-2-wittig-rearrangement-and-the-mechanistic-proposal-revisited
#20
Rocío Velasco, Carlos Silva López, Olalla Nieto Faza, Roberto Sanz
By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α-lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]-Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α-lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups...
October 10, 2016: Chemistry: a European Journal
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