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Nai-Wei Liu, Kamil Hofman, André Herbert, Georg Manolikakes
An efficient cross-coupling of sodium or lithium sulfinates with aryl iodides, using a combination of nickel and photoredox catalysis, is described. The dual catalyst system enables a versatile synthesis of aryl sulfones at room temperature in good yields and displays a broad functional group compatibility. The potential utility of this method in the late-stage diversification of complex molecules and in the conversion of organolithium reagents and sulfur dioxide into sulfones is demonstrated.
January 16, 2018: Organic Letters
Daniel Wilson, Alexander Hinz, Jose Manuel Goicoechea
The synthesis and characterization of a stable phosphaethynolato-borane, [B]OCP (1, [B] = N,N'-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl), is described. The increased triple bond character of the P-C bond in 1 relative to the free ion (PCO-) is probed in a series of reactivity studies. Compound 1 readily dimerises in donor solvents to afford a cyclic five-membered 6π-aromatic compound, cyclo-P2{C[B]}O{CO[B]} (2), which decarbonylates on UV irradiation. By contrast the nickel-mediated dimerisation of 1 affords the isomeric diphosphacyclobutene [P(CO[B])]2...
January 8, 2018: Angewandte Chemie
K Barry Sharpless, Bing Gao, Suhua Li, Peng Wu, John E Moses
Thionyl tetrafluoride (SOF4) is a valuable connective gas for sulfur fluoride exchange (SuFEx) click chemistry, that enables multidimensional linkages to be created via sulfur-oxygen (S-O) and sulfur-nitrogen (S-N) bonds. In this report, we expand the available SuFEx chemistry of SOF4 to include organolithium nucleophiles, and demonstrate, for the first time, the controlled projection of sulfur-carbon links at the sulfur center of SOF4-derived iminosulfur oxydifluorides (R1-N=SOF2). This protocol enables rapid and modular access to sulfonimidoyl fluorides [R1-N=SOFR2], another array of versatile SuFEx connectors with readily tunable reactivity of the S-F handle...
January 4, 2018: Angewandte Chemie
Eva Hevia, Maria J Rodriguez-Alvarez, Joaquin Garcia-Alvarez, Marina Uzelac, Michael Fairley, Charles T O'Hara
Edging closer towards developing air and moisture compatible polar organometallic chemistry, the chemoselective and ultrafast addition of a range of aryllithium reagents to nitriles has been accomplished using glycerol as a solvent, at room temperature in the presence of air, establishing a novel sustainable access to aromatic ketones. Addition reactions occur heterogeneously "on glycerol conditions", where the lack of solubility of the nitriles in glycerol and the ability of the latter to form strong intramolecular H-bonds seem key to favouring nucleophilic addition over competitive hydrolysis...
November 27, 2017: Chemistry: a European Journal
Dominic Auerhammer, Merle Arrowsmith, Holger Braunschweig, Rian D Dewhurst, J Oscar C Jiménez-Halla, Thomas Kupfer
The reaction of [(cAAC(Me))BH3] (cAAC(Me) = 1-(2,6-(i)Pr2C6H3)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) with a range of organolithium compounds led to the exclusive formation of the corresponding (dihydro)organoborates, Li(+)[(cAAC(Me)H)BH2R](-) (R = sp(3)-, sp(2)-, or sp-hybridised organic substituent), by migration of one boron-bound hydrogen atom to the adjacent carbene carbon of the cAAC ligand. A subsequent deprotonation/salt metathesis reaction with Me3SiCl or spontaneous LiH elimination yielded the neutral cAAC-supported mono(organo)boranes, [(cAAC(Me))BH2R]...
October 1, 2017: Chemical Science
Taichi Kano, Yusuke Aota, Keiji Maruoka
Chiral α-tertiary amines, which contain a tetrasubstituted carbon atom bearing one nitrogen atom and three different carbon substituents, are important but less accessible structural motifs of natural products and medicines. Most of these materials are synthesized conventionally through stereoselective addition of carbon nucleophiles to single geometric isomers of ketimines, whose two carbon substituents requires significant difference in size for high levels of stereoselection, under the influence of chiral catalysts or chiral auxiliaries...
November 6, 2017: Angewandte Chemie
Mingshuo Zeng, Stephen K Murphy, Seth B Herzon
We describe the development of an enantioselective synthetic route to (+)-pleuromutilin (1), (+)-12-epi-mutilin, and related derivatives. A key hydrindanone was prepared in three steps and 48% overall yield from cyclohex-2-en-1-one. 1,4-Hydrocyanation provided a nitrile (53%, or 85% based on recovered starting material) that was converted to the eneimide 57 in 80% yield by the 1,2-addition of methyllithium to the nitrile function, cyclization, and in situ acylation with di-tert-butyldicarbonate. The eneimide 57 was employed in a 2-fold neopentylic coupling reaction with an organolithium reagent derived from the alkyl iodides (R)- or (S)-30, which contain the C11-C13 atoms of the target, to provide diastereomeric diketones in 60% or 48% yield (for coupling with (R)- or (S)-30, respectively)...
November 15, 2017: Journal of the American Chemical Society
Cristina García-Ruiz, Jack L-Y Chen, Christopher Sandford, Kathryn Feeney, Paula Lorenzo, Guillaume Berionni, Herbert Mayr, Varinder K Aggarwal
Allylboronic esters react readily with carbonyls and imines (π-electrophiles), but are unreactive toward a range of other electrophiles. By addition of an aryllithium, the corresponding allylboronate complexes display enhanced nucleophilicity, enabling addition to a range of electrophiles (tropylium, benzodithiolylium, activated pyridines, Eschenmoser's salt, Togni's reagent, Selectfluor, diisopropyl azodicarboxylate (DIAD), MeSX) in high regio- and stereocontrol. This protocol provides access to key new functionalities, including quaternary stereogenic centers bearing moieties such as fluorine and the trifluoromethyl group...
November 1, 2017: Journal of the American Chemical Society
Florian F Mulks, Shirin Faraji, Frank Rominger, Andreas Dreuw, A Stephen K Hashmi
The synthesis and characterization of (NHC)(tricyclo[,7) ]hept-1-yl)gold(I) compounds is reported. Several of these organometallic compounds could be obtained by transmetalation from the organolithium precursor to the corresponding (NHC)gold(I) chlorides. These are by far the most strained stable organogold compounds reported so far. With these new compounds we were able to efficiently and selectively accomplish the first gold-catalyzed rearrangement of organogold compounds, even better yields were obtained by the first rhodium-catalyzed rearrangement of these organogold species...
October 4, 2017: Chemistry: a European Journal
Minh H Nguyen, Kevin T O'Brien, Amos B Smith
The initial design, synthesis, and validation of polymer-supported siloxane transfer agents have been achieved that permit the direct use of organolithium reagents in the palladium-catalyzed cross-coupling reactions. Through rational design, two generations of polymer support were developed that significantly simplify product purification and the transfer agent recycling.
October 20, 2017: Journal of Organic Chemistry
Alexander P Pulis, Ana Varela, Cinzia Citti, Pradip Songara, Daniele Leonori, Varinder K Aggarwal
Nonstabilized α-O-substituted tertiary organolithium species are difficult to generate, and the α-S-substituted analogues are configurationally unstable. We now report that they can both be generated easily and trapped with a range of electrophiles with high enantioselectivity, providing ready access to a range of enantioenriched tertiary alcohols and thiols. The configurational stability of the α-S-organolithium species was enhanced by using a less coordinating solvent and short reaction times.
August 28, 2017: Angewandte Chemie
Sonia Bruña, Ana Mª González-Vadillo, Marta Ferrández, Josefina Perles, M Merced Montero-Campillo, Otilia Mó, Isabel Cuadrado
The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc2(CH3)3C(CH2)2SiCH[double bond, length as m-dash]CH2 (5), Fc2(CH2[double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH2 (6), Fc2(OH)SiCH[double bond, length as m-dash]CH2 (7), Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH2)Fc2 (8) and Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-SiFc3 (9) is described...
September 12, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Kantapat Chansaenpak, Mengxi Yang, François P Gabbaï
With the synthesis of ortho-phenylene phosphino-tritylium cations as an objective, we generated (2-lithiophenyl)diphenylphosphine and (2-lithiophenyl)di-isopropylphosphine and allowed these organolithium reagents to react with benzophenone. The resulting phosphino-triarylcarbinols were allowed to react with HBF4 in the presence of trifluoroacetic anhydride in order to generate the corresponding cations. Instead of the targeted ortho-phenylene phosphino-tritylium, the cations formed in these reactions were identified as the four-membered phosphonium species 7,7-bis(phenyl)-8,8-bis(phenyl)-7-phosphoniabicyclo[4...
August 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Vittorio Pace, Laura Castoldi, Eugenia Mazzeo, Marta Rui, Thierry Langer, Wolfgang Holzer
β,γ-Unsaturated aldehydes with all-carbon quaternary or tertiary α-centers were rapidly assembled from ketones through a unique synthetic operation consisting of 1) C1 homologation, 2) Lewis acid mediated epoxide-aldehyde isomerization, and 3) electrophilic trapping. The synthetic equivalence of a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept of this previously undisclosed tactic. Mechanistic studies and labeling experiments suggest that an aldehyde enolate is a crucial intermediate...
October 2, 2017: Angewandte Chemie
Jonathan M E Hughes, James L Gleason
The total synthesis of (-)-virosaine A (1) was achieved in ten steps starting from furan and 2-bromoacrolein. A one-pot Diels-Alder cycloaddition/organolithium addition initiated an efficient sequence to access a key oxime/epoxide intermediate. Heating this intermediate in acetic acid resulted in an intramolecular epoxide opening/nitrone [3+2] cycloaddition cascade to construct the caged core of 1 in a single step. Several methods of C-H functionalization were assessed on the cascade product, and ultimately, a directed lithiation/bromination effected selective C14 functionalization, enabling the synthesis of 1...
August 28, 2017: Angewandte Chemie
Giuseppe Dilauro, Marzia Dell'Aera, Paola Vitale, Vito Capriati, Filippo Maria Perna
In contrast to classic methods carried out under inert atmospheres with dry volatile organic solvents and often low temperatures, the addition of highly polar organometallic compounds to non-activated imines and nitriles proceeds quickly, efficiently, and chemoselectively with a broad range of substrates at room temperature and under air with water as the only reaction medium. Secondary amines and tertiary carbinamines are furnished in yields of up to and over 99 %. The significant solvent D/H isotope effect observed for the on-water nucleophilic additions of organolithium compounds to imines suggests that the on-water catalysis arises from proton transfer across the organic-water interface...
July 11, 2017: Angewandte Chemie
Ioana Knopf, Daniel Tofan, Dirk Beetstra, Abdulaziz Al-Nezari, Khalid Al-Bahily, Christopher C Cummins
A family of cis-macrocyclic diphosphines was prepared in just three steps from white phosphorus and commercial materials using a modular synthetic approach. Alkylation of bicyclic diphosphane 3,4,8,9-tetramethyl-1,6-diphosphabicyclo(4.4.0)deca-3,8-diene, or P2(dmb)2, produced phosphino-phosphonium salts [R-P2(dmb)2]X, where R is methyl, benzyl and isobutyl, in yields of 90-96%. Treatment of these salts with organolithium or Grignard reagents yielded symmetric and unsymmetric macrocyclic diphosphines of the form cis-1-R-6-R'-3,4,8,9-tetramethyl-2,5,7,10-tetrahydro-1,6-DiPhospheCine, or R,R'-DPC, in which R' is methyl, cyclohexyl, phenyl or mesityl, in yields of 46-94%...
February 1, 2017: Chemical Science
Onkei Tai, Russell Hopson, Paul G Williard
We report the direct measurement of ligand-binding constants of organolithium complexes using a (1)H NMR/diffusion-ordered NMR spectroscopy (DOSY) titration technique. Lithium hexamethyldisilazide complexes with ethereal and ester donor ligands (THF, diethyl ether, MTBE, THP, tert-butyl acetate) are characterized using (1)H NMR and X-ray crystallography. Their aggregation and solvation states are confirmed using diffusion coefficient-formula weight correlation analysis, and the (1)H NMR/DOSY titration technique is applied to obtain their binding constants...
June 8, 2017: Journal of Organic Chemistry
Stephan G Koller, Jonathan O Bauer, Carsten Strohmann
Selective cleavage of a silicon-carbon bond in tetraorganosilanes is still a great challenge. A new type of Si-C(sp(3) ) bond cleavage in bench-stable (aminomethyl)silanes with common organolithium reagents as nucleophiles has now been identified. Suitable leaving groups are benzyl, allyl, and phenylthiomethyl groups. A β-donor function and polar solvents are essential for the reaction. Simple switching between α-deprotonation and substitution is possible through slight modifications of the reaction conditions...
June 26, 2017: Angewandte Chemie
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
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