cas 92273-73-9, BUTYLZINC BROMIDE | Articles data

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A Nickel(II)-Mediated Thiocarbonylation Strategy for Carbon Isotope Labeling of Aliphatic Carboxamides
A series of pharmaceutically relevant small molecules and biopharmaceuticals bearing aliphatic carboxamides have been successfully labeled with carbon-13. Key to the success of this novel carbon isotope labeling technique is the observation that 13C-labeled NiII-acyl complexes, formed from a 13CO insertion step with NiII-alkyl intermediates, rapidly react in less than one minute with 2,2’-dipyridyl disulfide to quantitatively form the corresponding 2-pyridyl thioesters. Either the use of 13C-SilaCOgen or 13C-COgen allows for the stoichiometric addition of isotopically labeled carbon monoxide. Subsequent one-pot acylation of a series of structurally diverse amines provides the desired 13C-labeled carboxamides in good yields. A single electron transfer pathway is proposed between the NiII-acyl complexes and the disulfide providing a reactive NiIII-acyl sulfide intermediate, which rapidly undergoes reductive elimination to the desired thioester. By further optimization of the reaction parameters, reaction times down to only 11 min were identified, opening up the possibility of exploring this chemistry for carbon-11 isotope labeling. Finally, this isotope labeling strategy could be adapted to the synthesis of 13C-labeled liraglutide and insulin degludec, representing two antidiabetic drugs.
Pedersen, Simon S.,Donslund, Aske S.,Mikkelsen, Jesper H.,Bakholm, Oskar S.,Papp, Florian,Jensen, Kim B.,Gustafsson, Magnus B. F.,Skrydstrup, Troels
supporting information
p. 7114 - 7123
(2021/03/03)

Palladium-catalysed regio- And stereoselective arylative substitution of γ,δ-epoxy-α,β-unsaturated esters and amides by sodium tetraaryl borates
Palladium-catalysed reactions of γ,δ-epoxy-α,β-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. A
Artok, Levent,Bilgi, Yasemin,Ku?, Melih
supporting information
p. 6378 - 6383
(2020/09/07)

Role of Electron-Deficient Olefin Ligands in a Ni-Catalyzed Aziridine Cross-Coupling to Generate Quaternary Carbons
We previously reported the development of an electron-deficient olefin (EDO) ligand, Fro-DO, that promotes the generation of quaternary carbon centers via Ni-catalyzed Csp3-Csp3 cross-coupling with aziridines. By contrast, electronically and structurally similar EDO ligands such as dimethyl fumarate and electron-deficient styrenes afford primarily β-hydride elimination side reactivity. Only a few catalyst systems have been identified that promote the formation of quaternary carbons via Ni-catalyzed Csp3-Csp3 cross-coupling. Although Fro-DO represents a promising ligand in this regard, the basis for its superior performance is not well understood. Here we describe a detailed mechanistic study of the aziridine cross-coupling reaction and the role of EDO ligands in facilitating Csp3-Csp3 bond formation. This analysis reveals that cross-coupling proceeds by a Ni0/II cycle with a NiII azametallacyclobutane catalyst resting state. Turnover-limiting C-C reductive elimination occurs from a spectroscopically observable NiII-dialkyl intermediate bound to the EDO. Computational analysis shows that Fro-DO accelerates turnover limiting reductive elimination via LUMO lowering. However, it is no more effective than dimethyl fumarate at reducing the barrier to Csp3-Csp3 reductive elimination. Instead, Fro-DO's unique reactivity arises from its ability to associate favorably to NiII intermediates. Natural bond order second-order perturbation theory analysis of the catalytically relevant NiII intermediate indicates that Fro-DO binds to NiII through an additional stabilizing donor-acceptor interaction between its sulfonyl group and NiII. Design of new ligands to evaluate this proposal supports this model and has led to the development of a new and tunable ligand framework.
Estrada, Jesús G.,Williams, Wendy L.,Ting, Stephen I.,Doyle, Abigail G.
supporting information
p. 8928 - 8937
(2020/05/13)

Csp3-Csp3 Bond-Forming Reductive Elimination from Well-Defined Copper(III) Complexes
Carbon-carbon bond-forming reductive elimination from elusive organocopper(III) complexes has been considered the key step in many copper-catalyzed and organocuprate reactions. However, organocopper(III) complexes with well-defined structures that can undergo reductive elimination are extremely rare, especially for the formation of Csp3-Csp3 bonds. We report herein a general method for the synthesis of a series of [alkyl-CuIII-(CF3)3]- complexes, the structures of which have been unequivocally characterized by NMR spectroscopy, mass spectrometry, and X-ray crystal diffraction. At elevated temperature, these complexes undergo reductive elimination following first-order kinetics, forming alkyl-CF3 products with good yields (up to 91%). Both kinetic studies and DFT calculations indicate that the reductive elimination to form Csp3-CF3 bonds proceeds through a concerted transition state, with a ΔH? = 20 kcal/mol barrier.
Paeth, Matthew,Tyndall, Sam B.,Chen, Liang-Yu,Hong, Jia-Cheng,Carson, William P.,Liu, Xingwu,Sun, Xiaodong,Liu, Jinjia,Yang, Kundi,Hale, Elizabeth M.,Tierney, David L.,Liu, Bin,Cao, Zhi,Cheng, Mu-Jeng,Goddard, William A.,Liu, Wei
supporting information
p. 3153 - 3159
(2019/03/06)

The Role of LiBr and ZnBr2 on the Cross-Coupling of Aryl Bromides with Bu2Zn or BuZnBr
The impact of LiBr and ZnBr2 salts on the Negishi coupling of alkylZnBr and dialkylzinc nucleophiles with both electron-rich and -poor aryl electrophiles has been examined. Focusing only on the more difficult coupling of deactivated (electron-rich) oxidative addition partners, LiBr promotes coupling with BuZnBr, but does not have such an effect with Bu2Zn. The presence of exogenous ZnBr2 shuts down the coupling of both BuZnBr and Bu2Zn, which has been shown before with alkyl electrophiles. Strikingly, the addition of LiBr to Bu2Zn reactions containing exogenous ZnBr2 now fully restores coupling to levels seen without any salt present. This suggests that there is a very important interaction between LiBr and ZnBr2. It is proposed that Lewis acid adducts are forming between ZnBr2 and the electron-rich Pd0 centre and the bromide from LiBr forms inorganic zincates that prevent the catalyst from binding to ZnBr2. This idea has been supported by catalyst design as chlorinating the backbone of the NHC ring of Pd-PEPPSI-IPent to produce Pd-PEPPSI-IPentCl catalyst now gives quantitative conversion, up from a ceiling of only 50 % with the former catalyst.
Eckert, Philip,Organ, Michael G.
supporting information
p. 15751 - 15754
(2019/11/16)

Efficient analoging around ethionamide to explore thioamides bioactivation pathways triggered by boosters in Mycobacterium tuberculosis
Ethionamide is a key antibiotic prodrug of the second-line chemotherapy regimen to treat tuberculosis. It targets the biosynthesis of mycolic acids thanks to a mycobacterial bioactivation carried out by the Baeyer-Villiger monooxygenase EthA, under the control of a transcriptional repressor called EthR. Recently, the drug-like molecule SMARt-420, which triggers a new transcriptional regulator called EthR2, allowed the derepression a cryptic alternative bioactivation pathway of ethionamide. In order to study the bioactivation of a collection of thioisonicotinamides through the two bioactivation pathways, we developed a new two-step chemical pathway that led to the efficient synthesis of eighteen ethionamide analogues. Measurements of the antimycobacterial activity of these derivatives, used alone and in combination with boosters BDM41906 or SMARt-420, suggest that the two different bioactivation pathways proceed via the same mechanism, which implies the formation of similar metabolites. In addition, an electrochemical study of the aliphatic thioisonicotinamide analogues was undertaken to see whether their oxidation potential correlates with their antitubercular activity measured in the presence or in the absence of the two boosters.
Prieri, Marion,Frita, Rosangela,Probst, Nicolas,Sournia-Saquet, Alix,Bourotte, Marilyne,Déprez, Benoit,Baulard, Alain R.,Willand, Nicolas
p. 35 - 46
(2018/10/02)

Palladium-Catalyzed Cross-Coupling of Silyl Electrophiles with Alkylzinc Halides: A Silyl-Negishi Reaction
We report the first example of a silyl-Negishi reaction between secondary zinc organometallics and silicon electrophiles. This palladium-catalyzed process provides direct access to alkyl silanes. The delicate balance of steric and electronic parameters of the employed DrewPhos ligand is paramount to suppressing isomerization and promoting efficient and selective cross-coupling.
Cinderella, Andrew P.,Vulovic, Bojan,Watson, Donald A.
supporting information
p. 7741 - 7744
(2017/06/21)

Docking study and biological evaluation of pyrrolidine-based iminosugars as pharmacological chaperones for Gaucher disease
We report on the synthesis and biological evaluation of a series of α-1-C-alkylated 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) derivatives as pharmacological chaperones for Gaucher disease. The parent compound, DAB, did not show inhibition of human β-glucocerebrosidase but showed moderate intestinal α-glucosidase inhibition; in contrast, extension of α-1-C-alkyl chain length gave a series of highly potent and selective inhibitors of the β-glucocerebrosidase. Our design of α-1-C-tridecyl-DAB (5j) produced a potent inhibitor of the β-glucocerebrosidase, with IC50 value of 0.77 μM. A molecular docking study revealed that the α-1-C-tridecyl group has a favorable interaction with the hydrophobic pocket and the sugar analogue part (DAB) interacted with essential hydrogen bonds formed to Asp127, Glu235 and Glu340. Furthermore, α-1-C-tridecyl-DAB (5j) displayed enhancement of activity at an effective concentration 10-times lower than isofagomine. α-1-C-Tridecyl-DAB therefore provides the first example of a pyrrolidine iminosugar as a new class of promising pharmacological chaperones with the potential for treatment of Gaucher disease. 2016 The Royal Society of Chemistry.
Kato, Atsushi,Nakagome, Izumi,Sato, Kasumi,Yamamoto, Arisa,Adachi, Isao,Nash, Robert J.,Fleet, George W. J.,Natori, Yoshihiro,Watanabe, Yasuka,Imahori, Tatsushi,Yoshimura, Yuichi,Takahata, Hiroki,Hirono, Shuichi
p. 1039 - 1048
(2016/01/20)

Electron-deficient olefin ligands enable generation of quaternary carbons by Ni-catalyzed cross-coupling
A Ni-catalyzed Negishi cross-coupling with 1,1-disubstituted styrenyl aziridines has been developed. This method delivers valuable β-substituted phenethylamines via a challenging reductive elimination that affords a quaternary carbon. A novel electron-deficient olefin ligand, Fro-DO, proved crucial for achieving high rates and chemoselectivity for C-C bond formation over β-H elimination. This ligand is easy to access, is stable, and presents a modular framework for reaction discovery and optimization. We expect that these attributes, combined with the fact that the ligands impart distinct electronic properties to a metal, will support the invention of new transformations not previously possible using established ligands.
Huang, Chung-Yang,Doyle, Abigail G.
supporting information
p. 5638 - 5641
(2015/05/20)

The palladium-catalyzed anti-Markovnikov hydroalkylation of allylic alcohol derivatives
A palladium-catalyzed hydroalkylation reaction of protected allylic alcohols using alkylzinc bromide reagents is reported. This account includes numerous allylic, homoallylic, and bishomoallylic alcohol derivatives, all with a uniform selectivity of >20:1
DeLuca, Ryan J.,Sigman, Matthew S.
supporting information
p. 92 - 95
(2013/03/28)

Directed nickel-catalyzed negishi cross coupling of alkyl aziridines
Herein we report a nickel-catalyzed C-C bond-forming reaction between simple alkyl aziridines and organozinc reagents. This method represents the first catalytic cross-coupling reaction employing a nonallylic and nonbenzylic Csp3-N bond as an electrophile. Key to its success is the use of a new N-protecting group (cinsyl or Cn) bearing an electron-deficient olefin that directs oxidative addition and facilitates reductive elimination. Studies pertinent to elucidation of the mechanism of cross coupling are also presented.
Nielsen, Daniel K.,Huang, Chung-Yang,Doyle, Abigail G.
supporting information
p. 13605 - 13609
(2013/09/24)

α-1-C-Butyl-1,4-Dideoxy-1,4-Imino-L-Arabinitol as a second-Generation iminosugar-based oral α-Glucosidase inhibitor for improving postprandial hyperglycemia
We report on the synthesis and the biological evaluation of a series of α-1-C-alkylated 1,4-dideoxy-1,4-imino-l-arabinitol (LAB) derivatives. The asymmetric synthesis of the derivatives was achieved by asymmetric allylic alkylation, ring-closing metathesis, and Negishi cross-coupling as key reactions. α-1-C-Butyl-LAB is a potent inhibitor of intestinal maltase, isomaltase, and sucrase, with IC50 values of 0.13, 4.7, and 0.032 μM, respectively. Matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis revealed that this compound differs from miglitol in that it does not influence oligosaccharide processing and the maturation of glycoproteins. A molecular docking study of maltase-glucoamylase suggested that the interaction modes and the orientations of α-1-C-butyl-LAB and miglitol are clearly different. Furthermore, α-1-C-butyl-LAB strongly suppressed postprandial hyperglycemia at an early phase, similar to miglitol in vivo. It is noteworthy that the effective dose was about 10-fold lower than that for miglitol. α-1-C-Butyl-LAB therefore represents a new class of promising compounds that can improve postprandial hyperglycemia.
Kato, Atsushi,Hayashi, Erina,Miyauchi, Saori,Adachi, Isao,Imahori, Tatsushi,Natori, Yoshihiro,Yoshimura, Yuichi,Nash, Robert J.,Shimaoka, Hideyuki,Nakagome, Izumi,Koseki, Jun,Hirono, Shuichi,Takahata, Hiroki
p. 10347 - 10362
(2013/02/23)

Lithium organozincate complexes LiRZnX2: Common species in organozinc chemistry
We have used a combination of electrospray ionization (ESI) mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to investigate the effect of LiCl on solutions of organylzinc halides RZnX (R = Bu, Bn, Ph; X = halogen) and dibutylzinc Bu2Zn in tetrahydrofuran. In the case of RZnX, the addition of LiX (X = Cl) leads to a steep rise of the ESI signal intensities of RZnX2- organozincate anions. At the same time, the electrical conductivities strongly increase and the NMR absorptions of the α-H atoms of BuZnX shift upfield. These results consistently point to the formation of lithium organozincates Li +RZnX2-. As the most common syntheses of RZnX reagents involve stoichiometric amounts of LiX salts, Li+RZnX 2- complexes are supposedly widespread and may hold the key to understanding the marked effects of LiCl on the reactivity of organozinc halides. In contrast, we find Bu2Zn to have a much lower tendency to add LiCl and form ate complexes. This result is in line with the weak effect of LiCl on the reactivity of diorganozinc compounds reported in the literature.
Fleckenstein, Julia E.,Koszinowski, Konrad
p. 5018 - 5026
(2011/11/07)

Overriding felkin control: A general method for highly diastereoselective chelation-controlled additions to α-silyloxy aldehydes
According to the Felkin-Anh and Cram-chelation models, nucleophilic additions to α-silyloxy aldehydes proceed through a nonchelation pathway due to the steric and electronic properties of the silyl group, giving rise to Felkin addition products. Herein we describe a general method to promote chelationcontrol in additions to α-silyloxy aldehydes. Dialkylzincs, functionalized dialkylzincs, and (E)-disubstituted, (E)-trisubstituted, and (Z)-disubstituted vinylzinc reagents add to silyl-protected α-hydroxy aldehydes with high selectivity for chelation-controlled products (dr of 10:1 to 20:1) in the presence of alkylzinc halides or triflates, RZnX. With the high functional group tolerance of organozinc reagents, the mild Lewis acidity of RZnX, and the excellent diastereoselectivities favoring the chelation-controlled products, this method will be useful in the synthesis of natural products. A mechanism involving chelation is supported by (1) NMR studies of a model substrate, (2) a dramatic increase in reaction rate in the presence of an alkylzinc halide, and (3) higher diastereoselectivity with larger alkyl substituents on the α-carbon of the aldehyde. This method provides access to chelation-controlled addition products with high diastereoselectivity previously unavailable using achiral organometallic reagents.
Stanton, Gretchen R.,Johnson, Corinne N.,Walsh, Patrick J.
p. 4399 - 4408
(2010/06/14)

Highly reactive zinc form, method for the production thereof, and use of the same
The invention relates to a highly reactive zinc form, to a method for the production thereof, and to the use of said highly reactive zinc form in synthetic chemistry.
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(2009/05/28)

Formation of coordinated RZn(macrocycle)+ cations and organozincate anions from reactions of organozinc compounds and macrocycles
An RZnZ compound (R = alkyl) and a macrocycle react in benzene to form RZn(macrocycle)+ ions when the macrocycle is an effective coordinator for RZn+ and Z- can exist as the anion or become attached to an organometallic acceptor to form an organometalate anion. R2Zn and R3Al form RZn(macrocycle)+R4Al- with 14N4 (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) 15N5 (1,4,7,10,13-pentamethyl-1,4,7,10,13-pentaazacyclopentadecane), 2,1,1-cryptand, or 2,2,1-cryptand but not with 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclo-octadecane, 2,2,2-cryptand, 15-crown-5, or 18-crown-6. RZnZ, R2Zn, and 14N4 form RZn(14N4)+R2ZnZ- when Z is Cl, Br, I, or 3,5-di-tert-butylphenoxy but not when Z is tert-butoxy. Various combinations of RZnZ with Z = Cl, Br, I, 2,6-di-tert-butylphenoxy, or 3,5-di-tert-butylphenoxy and 14N4, 15N5, 2,1,1-cryptand, or 2,2,1-cryptand form RZn(macrocycle)+Z- solids; solids do not form when Z is methoxy or tert-butoxy nor when the macrocycle is 12-crown-4, 15-crown-5, or 18-crown-6.
Fabicon, Ronaldo M.,Richey Jr., Herman G.
p. 4018 - 4023
(2008/10/08)

Synthese et reactivite de quelques organozinciques dans des solvants peu courants en chimie organometallique
The use of solvents strange to organometallic chemistry viz. carbonic or phosphoric esters, or sulfolane allows zinc to react with organic halides, which are usually unreactive towards this metal.The ractions of the organozinc compounds thus synthesised (
Grodin, Joseph,Sebban, Mohammed,Vottero, Philippe,Blancou, Hubert,Commeyras, Auguste
p. 237 - 242
(2007/10/02)