- Asymmetric Hydroboration of Heteroaryl Ketones by Aluminum Catalysis
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A series of methyl aluminum complexes bearing chiral biphenol-type ligands were found to be highly active catalysts in the asymmetric reduction of heterocyclic ketones (S/C = 100-500, ee up to 99%). The protocol is suitable for a wide range of substrates and has a high tolerance to functional groups. The formed 2-heterocyclic-alcohols are valuable building blocks in drug discovery or can be used as ligands in asymmetric catalysis. Isolation and comprehensive characterization of the reaction intermediates support a catalysis cycle proposed by DFT calculations.
- Lebedev, Yury,Polishchuk, Iuliia,Maity, Bholanath,Dinis Veloso Guerreiro, Miguel,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 19415 - 19423
(2019/12/24)
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- Synthesis of 2,5-di(hydroxyalkyl)-1,3-thiazoles
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A general approach towards synthesis of 2(5)-hydroxyalkyl-substituted 1,3-thiazole derivatives has been proposed. The method includes lithiation of 1,3-thiazole ring followed by reacting the formed thiazole lithium derivatives with electrophiles.
- Sinenko,Slivchuk,Bal'On, Ya. G.,Brovarets
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p. 1855 - 1861
(2015/10/12)
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- Ruthenium catalyzed hydrohydroxyalkylation of isoprene with heteroaromatic secondary alcohols: Isolation and reversible formation of the putative metallacycle intermediate
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Heteroaromatic secondary alcohols react with isoprene to form products of hydrohydroxyalkylation in the presence of ruthenium(0) catalysts generated from Ru3(CO)12 and tricyclohexylphosphine, enabling direct conversion of secondary to tertiary alcohols in the absence of premetalated reagents or stoichiometric byproducts. The putative oxaruthenacycle intermediate has been isolated and characterized, and reversible metallacycle formation has been demonstrated.
- Park, Boyoung Y.,Montgomery, T. Patrick,Garza, Victoria J.,Krische, Michael J.
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supporting information
p. 16320 - 16323
(2013/12/04)
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- PREPARATION AND USE OF MAGNESIUM AMIDES
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The present application relates to mixed Mg/Li amides of the general formula R1R2N-Mg-NR3R4.zLiY (II) wherein R1, R2, R3, and R4 are, independently, selected from H, substituted or unsubstituted aryl or heteroaryl containing one or more heteroatoms, linear, branched or cyclic, substituted or unsubstituted alkyl, alkenyl, alkynyl, or silyl derivatives thereof; and R1 and R2 together, or R3 and R4 together can be part of a cyclic or polymeric structure; and wherein at least one of R1 and R2 and at least one of R3 and R4 is other than H; Y is selected from the group consisting of F; Cl; Br; I; CN; SCN; NCO; HaIOn, wherein n = 3 or 4 and Hal is selected from Ci, Br and I; NO3; BF4; PF6; H; a carboxylate of the general formula RxCO2; an alcoholate of the general formula ORx; a thiolate of the general formula SRx; RxP(O)O2; or SCORx; or SCSRx; OnSRx, wherein n = 2 or 3; or NOn, wherein n = 2 or 3; and a derivative thereof; wherein Rx is a substituted or unsubstituted aryl or heteroaryl containing one or more heteroatoms, linear, branched or cyclic, substituted or unsubstituted alkyl, alkenyl, alkynyl, or derivatives thereof, or H; m is O or 1; and z > 1; as well as a process for the preparation of the mixed Mg/Li amides and the use of these amides, e.g. as bases.
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Page/Page column 27
(2008/12/07)
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- Preparation and use of magnesium amides
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The present application relates to mixed Mg/Li amides of the general formula ???????? R1R2N-MgX·zLiY?????(I), wherein R1, R2 and R3 independently are selected from substituted or unsubstituted aryl or heteroaryl containing one or more heteroatoms, linear, branched or cyclic, substituted or unsubstituted alkyl, alkenyl, alkynyl, or derivatives thereof, and, for R1 and R2 only, the silyl derivatives thereof; one of R1 and R2 may be H; or R1 and R2 together can be part of a cyclic or polymeric structure; X and Y independently are selected amongst others from the group consisting of F; Cl; Br; I; CN; SCN; NCO; and z > 0, as well as a process for the preparation of the mixed Mg/Li amides and the use of these amides, e.g. as bases.
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Page/Page column 4; 7-8
(2008/06/13)
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- Mixed Mg/Li amides of the type R2NMgCl·LiCl as highly efficient bases for the regioselective generation of functionalized aryl and heteroaryl magnesium compounds
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(Chemical Equation Presented) Two are better than one: Mixed lithium-magnesium complexes of the type R2NMgCl·LiCl are kinetically highly active bases that convert a range of polyfunctional aromatic and heteroaromatic substrates into the corresponding magnesiated derivatives with high regioselectivity.
- Krasovskiy, Arkady,Krasovskaya, Valeria,Knochel, Paul
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p. 2958 - 2961
(2007/10/03)
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- Method of preparing organomagnesium compounds
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The present invention is directed to a reagent for use in the preparation of organomagnesium compounds as well as to a method of preparing such organomagnesium compounds. The present invention furthermore provides a method of preparing functionalized or unfunctionalized organic compounds as well as the use of the reagents of the present invention in the preparation of organometallic compounds and their reaction with electrophiles. Finally, the present invention is directed to the use of lithium salts - LiY in the preparation of organometallic compounds and their reactions with electrophiles and to an organometallic compound which is obtainable by the disclosed method.
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Page/Page column 15
(2010/02/14)
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- Design, synthesis, and structure-activity relationships of pyrazolo[3,4-d]pyrimidines: A novel class of potent enterovirus inhibitors
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A series of pyrazolo[3,4-d]pyrimidines were synthesized and their antiviral activity was evaluated in a plaque reduction assay. It is very interesting that this class of compounds provide remarkable evidence that they are very specific for human enteroviruses, in particular, coxsackieviruses. Some derivatives proved to be highly effective in inhibiting enterovirus replication at nanomolar concentrations. SAR studies revealed that the phenyl group at the N-1 position and the hydrophobic diarylmethyl group at the piperazine largely influenced the in vitro antienteroviral activity of this new class of potent antiviral agents. It was found that the pyrazolo[3,4-d]pyrimidines with a thiophene substituent, such as compounds 20-24, in general exhibited high activity against coxsackievirus B3 (IC50=0.063-0.089μM) and moderate activity against enterovirus 71 (IC50=0.32-0.65μM) with no apparent cytotoxic effect toward RD (rhabdomyosarcoma) cell lines (CC5025μ M).
- Chern, Jyh-Haur,Shia, Kak-Shan,Hsu, Tsu-An,Tai, Chia-Liang,Lee, Chung-Chi,Lee, Yen-Chun,Chang, Chih-Shiang,Tseng, Sung-Nien,Shih, Shin-Ru
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p. 2519 - 2525
(2007/10/03)
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- A LiCl-mediated Br/Mg exchange reaction for the preparation of functionalized aryl- and heteroarylmagnesium compounds from organic bromides
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A wide range of aryl and heteroaryl bromides, which are usually sluggish in exchange reactions, are readily converted into the corresponding Grignard reagents by means of a Br/Mg exchange reaction triggered by iPrMgCl·LiCl (see scheme). These Grignard intermediates react with electrophiles in good yields.
- Krasovskiy, Arkady,Knochel, Paul
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p. 3333 - 3336
(2007/10/03)
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- The synthesis of 2-substituted azoles through a one-pot three-component reaction
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We have discovered a new reaction whereby 2-substituted azoles are formed in the reaction of an azolium ylide with reactive carbonyl compounds. These products contain a leaving group in the α-position, which on solvolysis in the presence of nucleophiles yield azoles with a variety of α-substituents. We have developed new aspects of this chemistry and expanded the scope to include imidazoles, thiazoles, benzimidazoles and triazoles, such that in two reaction steps a wide diversity of substitution patterns are obtained.
- Deng, Yijun,Hlasta, Dennis J.
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p. 189 - 192
(2007/10/03)
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- Stereoselective and competitive [1,2]- and [2,3]-wittig rearrangements of allyl heteroarylalkyl ethers
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Several allyl heteroarylalkyl ethers have been synthesized and then deprotonated with nBuLi in THF at -78°C to give lithium derivatives. The lithium-bearing terminus was either the α- or the α′-carbon atom, depending on the associated proton acidity. In the absence of an external electrophile, a sigmatropic rearrangement occurs, generating a new C-C bond. Heteroarylalkyl homoallylic alcohols and allyl heteroarylalkylic alcohols were obtained as products of stereoselective [2,3]- or [1,2]-Wittig rearrangements, respectively. Homoallylic alcohols were obtained in high yields and with fairly good enantiomeric enrichments when the reactions were carried out in toluene with (-)-sparteine as the external chiral ligand.
- Capriati, Vito,Florio, Saverio,Ingrosso, Giovanni,Granito, Catia,Troisi, Luigino
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p. 478 - 484
(2007/10/03)
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- Preparation of 2- and 5-aryl substituted thiazoles via palladium-catalyzed Negishi cross-coupling
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2-Aryl substituted thiazoles 3a-k were prepared by oxidative insertion of zinc into 2-bromothiazole (1) followed by palladium(0)-catalyzed Negishi cross-coupling in a one-pot procedure. 5-Aryl substituted thiazoles 6a-i were prepared by regioselective C-5 lithiation of 2-(trimethylsilyl)thiazole (4) followed by transmetalation with zinc chloride and palladium(0)-catalyzed Negishi cross-coupling in a one-pot procedure. The synthetic sequences were combined to give 2,5-diaryl substituted thiazoles 8a,b and 10 via stepwise C-2 and C-5 arylation and vice versa.
- Jensen,Skj?rb?k,Veds?
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p. 128 - 134
(2007/10/03)
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- Selective metallation of thiophene and thiazole rings with magnesium amide base
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The chemoselective magnesiation of thiophene and thiazole derivatives were reported using magnesium chloride. Organomagnesium compounds were used at relatively higher temperatures. The results showed that hydrogen-magnesium exchange reaction of thiophene derivatives with iPr2NMgCl proceeded selectively.
- Shilai, Manabu,Kondo, Yoshinori,Sakamoto, Takao
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p. 442 - 444
(2007/10/03)
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- Preparation of new polyfunctional magnesiated heterocycles using a chlorine-, bromine-, or iodine-magnesium exchange
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The reaction of heteroaryl iodides with i-PrMgBr (ca. 1.0 equiv) in THF provides the corresponding magnesiated heterocycles. Functional groups such as an ester, cyano, or chloride functions are tolerated in these new Grignard reagents if the exchange can be performed below -20 °C. This is the case for all heterocycles bearing electron-withdrawing groups or chelating functions facilitating the iodine-magnesium exchange. In many cases, the exchange can be extended to heteroaryl bromides, and a case of a chlorine-magnesium exchange is described with tetrachlorothiophene. This new preparation of functionalized heteroarylmagnesium compounds provides after reaction with various electrophiles a new entry to a broad range of polyfunctional pyridines, imidazoles, furanes, thiophenes, pyrroles, antipyrines, and uracil derivatives. The application of the halogenmagnesium exchange in the solid phase allows the performance of solid-phase synthesis, with potential applications for combinatorial chemistry.
- Abarbri, Mohamed,Thibonnet, Jerome,Berillon, Laurent,Dehmel, Florian,Rottlaender, Mario,Knochel, Paul
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p. 4618 - 4634
(2007/10/03)
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- An unusual oxidation of thiazol-2-ylmethanol in hydrolytic conditions
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The treatment of aryl and heteroaryl thiazol-2-ylmethanols with sulfuric acid in a dimethoxyethane-water mixture at 80 deg C gave the corresponding ketone as the only product in good yields. All the data are agreement with a mechanism involving the format
- D'Auria, Maurizio,Mauriello, Giacomo,Racioppi, Rocco
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- Bromine-magnesium-exchange as a general tool for the preparation of polyfunctional aryl and heteroaryl magnesium-reagents
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The scope of the Br-Mg-exchange reaction for the preparation of polyfunctional aryl and heteroaryl magnesium reagents has been studied. Various functional groups (ester, cyano, bromide) were tolerated in the exchange reaction allowing the preparation of polyfunctional Mg-reagents. Several dibromo- or tribromoheterocycles undergo a chemoselective mono-Br-Mg exchange leading to highly functionalized heterocycles.
- Abarbri, Mohamed,Dehmel, Florian,Knochel, Paul
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p. 7449 - 7453
(2007/10/03)
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- 1,2,3-TRIAZOLOTHIAZOLES; SYNTHESIS AND PROPERTIES
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The synthesis of 1,2,3-triazolothiazole (15) and its 3-methyl- (16) and 3-phenyl- (17) derivatives is reported, together with their spectra, quaternisation, and ring opening reactions.
- Jones, Gurnos,Ollivierre, Hermione,Fuller, L. S.,Young, J. H.
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p. 2851 - 2860
(2007/10/02)
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- Synthesis and Chromogenic Properties of Some Water-Soluble 5-Nitro-2-pyridylhydrazones
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Four new water-soluble hydrazones, α-(5-nitro-2-pyridyl)hydrazono-α-(2-quinolyl)-3-toluenesulfonic acid, α-(5-nitro-2-pyridyl)hydrazono-α-(2-thiazolyl)-3-toluenesulfonic acid, α-(2-benzothiazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid, and α-(2-benzimidazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid, were synthesized.Their proton dissociation constants were determined spectrophotometrically.The chromogenic properties of the synthesized hydrazones and their reactions with metal ions were investigated spectrophotometrically in detail.The results revealed that the synthesized hydrazones react with various metal ions including transition metal ions, especially with cadmium(II), nickel(II), and zinc(II) to form stable colored comoplexes with very large apparent molar absorptivities, so that their were found to be all very useful as highly sensitive spectrophotometric reagents.
- Ishi, Hajime,Odashima, Tsugikatsu,Kawamonzen, Yoshiaki,Katahira, Aoba-ku,Odashima, Tsugikatsu
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p. 3398 - 3404
(2007/10/02)
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- Synthesis of (Trimethylsilyl)thiazoles and Reactions with Carbonyl Compounds. Selectivity Aspects and Synthetic Utility
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Synthetic routes to all possible regioisomeric mono- and bis(trimethylsilyl)thiazoles as well as to the tris(trimethylsilyl) derivative via lithiation-silylation sequences of the thiazole ring followed by selective protodesilylation in some cases are described. (Trimethylsilyl)thiazoles serve as thiazolyl donor synthons upon reaction with carbonyl compounds (ketenes, acyl chlorides, aldehydes) for the preparation of mono- and bis-substituted thiazoles in very good yields.Carbodesilylation occurs more readily at the 2- than 5-position, whereas no reaction takes place at the 4-position.A mechanism via a thiazolium 2-ylide as an intermediate is suggested for the carbodesilylation at the 2-position.
- Dondoni, Alessandro,Fantin, Giancarlo,Fogagnolo, Marco,Medici, Alessandro,Pedrini, Paola
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p. 1748 - 1761
(2007/10/02)
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- NEW PERSPECTIVES IN THIAZOLE CHEMISTRY
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Carbon-carbon bond forming reactions at C-2 of the thiazole ring have been carried using two strategies, one involving the addition of organometallic reagents (lithium carbanions of esters, Grignard salts, silyl enol ethers, silyl ketene acetals, silylazoles) to N-acylthiazolium salts; the other involving the addition of carbon electrophiles (ketenes, acyl chlorides, anhydrides, aldehydes) to N-acylthiazolium ylides generated in situ.The reactions have been applied to 1,3-thiazole and 2-trimethylsilyl-1,3-thiazole, the latter being more reactive than the former toward electrophiles.This methodology constitutes a new entry to a variety of functionalized thiazoles and thiazolines which are potential building blocks for the synthesis of natural compounds and analogues of biologically active molecules (penems, arylpropionic acids).Some ring transformations of thiazoles induced by carbon-sulfur bond cleavage are also described.The fundamental role played by the sulfur atom of the thiazole ring in the observed reactions is pointed out and briefly discussed.
- Dondoni, Alessandro
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- REACTIONS OF 2-TRIMETHYLSILYLYHIAZOLE WITH ACYL CHLORIDES AND ALDEHYDES SYNTHESIS OF NEW THIAZOL-2-YL DERIVATES
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2-Trimethylsilylthiazole (1) undergoes ipso-substitution of the silyl group with various acyl chlorides and ethyl chloroformate affording 2-acylthiazoles (2)-(5) but adds by the carbon-silicon bond to the carbonyl group of aldehydes yielding thiazol-2-yl-trimethylsiloxy-methane derivates (7).
- Medici, Alessandro,Fantin, Giancarlo,Fogagnolo, Marco,Dondini, Alessandro
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p. 2901 - 2904
(2007/10/02)
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