Showing papers on "Alkylation published in 1998"
TL;DR: The chiral quaternary ammonium salt as mentioned in this paper serves as phase transfer catalyst for the enantioselective conversion of the glycine derivative 2 to a variety of cyclic and acyclic chiral α-amino acids with enanti-lectivities as high as 200:1 in alkylation and Michael addition reactions.
216 citations
Patent•
20 Jul 1998
TL;DR: In this article, the authors present a process for making modified alkylbenzenesulfonate surfactants and the products of such processes, including the surfactant compositions and consumer cleaning products, especially laundry detergents, containing them.
Abstract: The present invention is in the field of processes for making modified alkylbenzenesulfonate surfactants and of the products of such processes, including the surfactant compositions and consumer cleaning products, especially laundry detergents, containing them. The processes herein have in common: (a) the provision of a specific, lightly branched alcohol mixture and (b) alkylation reaction of benzene, toluene or the like with this alcohol mixture using specific shape-selective zeolite catalysts, preferably at least partially dealuminized nonfluoridated H-mordenites. The alcohol required in the process can be prepared by any of (i) selective hydroformylation of lightly branched olefins; (ii) nonselective hydroformylation of linear olefins; and (iii) reactions of suitable alkyl Grignard reagents with methyl alkyl ketones.
211 citations
TL;DR: A means to alkylate R-imino esters enantioselectively in up to 98% ee and in high chemical yields with enol silanes using chiral catalytic late transition metal phosphine complexes selected from Ag(I), Cu(I, Ni(II), and Pd(II) (eq 2).
Abstract: Over the past several years, highly effective methods for enantioselective aldol additions catalyzed by Lewis acids have been developed.1 Analogous alkylations of imines, however, have not been nearly as well studied nor as successful.2 R-Imino esters are almost unstudied in Lewis acid-catalyzed reactions,3 but are especially attractive imine substrates for the efficient syntheses of natural product precursors,4 pharmaceutically active compounds,5 and nonnatural amino acids;6 the last category has recently received much attention as peptidomimetics7 and in sitedirected mutagenesis studies.8 In a recent report, we demonstrated that select late transition metals can catalyze the cis-trans isomerization of prolyl peptides through simultaneous coordination of the metal to the amide nitrogen (Na) and the side chain carbonyl group (Figure 1, a).9 Catalysis fails to occur on simple amides that do not contain an additional binding site. These results prompted us to investigate whether analogous coordination of a transition metal to the nitrogen of a functionalized imine and a chelating carbonyl group could activate the substrate toward a highly enantioselective addition of nucleophiles (Figure 1, b). From our point of view, activated R-imino esters 1 seemed ideal substrates for Lewis acid catalyzed asymmetric alkylations for several reasons: (1) alkylation occurs readily at the imine carbon with a variety of nucleophiles, (2) the electron-withdrawing R-ester group provides additional activation of the imino group to nucleophilic attack, (3) the imine N and carbonyl O can form a stable five-membered chelate ring with a chiral Lewis acid catalyst (eq 1),10 providing additional rigidity to an activated complex and potentially enhanced product selectivity, and (4) alkylation of imine derivatives 1 with enol silane nucleophiles can lead to substituted γ-oxo R-amino acids (aspartic acid analogues) that comprise a class of interesting and useful biologically active natural compounds.11 We report herein a means to alkylate R-imino esters enantioselectively in up to 98% ee and in high chemical yields with enol silanes using chiral catalytic late transition metal phosphine complexes selected from Ag(I), Cu(I), Ni(II), and Pd(II) (eq 2).
206 citations
Patent•
20 Jul 1998TL;DR: In this article, a combination of delinearization and alkylation is proposed for making alkylbenzenesulfonate surfactants, which includes sulfonating, neutralizing and incorporating the resulting modified alkylsulfonates into consumer products.
Abstract: The present invention is in the field of processes for making alkylbenzenesulfonate surfactants. The processes herein include a combination of two essential steps, delinearization and alkylation. The delinearization step selected herein introduces particular types of limited branching into an aliphatic hydrocarbon having ten or more, but no more than about 16, carbon atoms. The hydrocarbon includes olefin having a hydrocarbon chain length suitable for detergent manufacture, e.g., C10-C14, or a corresponding paraffin. The second essential step is an alkylation step having an internal isomer selectivity of from 0 to no more than about 40 in which the hydrocarbon is used to monoalkylate benzene catalytically with an alkylation catalyst. Such alkylation catalysts preferably comprise an at least partially crystalline porous zeolite-containing solid, the zeolite having moderate acidity and intermediate pore size. Preferred alkylation catalysts include certain at least partially dealuminized acidic nonfluorinated mordenites. The processes herein further comprise sulfonating, neutralizing and incorporating the resulting modified alkylbenzenesulfonate surfactants into consumer products. The invention relates also to the products of the processes, including modified surfactants and consumer cleaning products containing them.
195 citations
TL;DR: The room temperature ionic liquid 1-butyl-3methylimidazolium hexafluorophosphate, [bmim][PF6], is used as a green, recyclable alternative to dipolar aprotic solvents for the regioselective alkylation at the heteroatom of indole and 2-naphthol as discussed by the authors.
192 citations
TL;DR: In this paper, the authors investigated the nonlinear properties of the asymmetric reaction of dimethylzinc and benzaldehyde in the presence of (2S)-3-exo-(dimethylamino)isoborneol [(2S]-DAIB] and showed that the enantiomeric purity of the product is much higher than that of the chiral source, DAIB, while the rate of enantioselective catalysis decreases considerably.
Abstract: Asymmetric reaction of dimethylzinc and benzaldehyde in the presence of (2S)-3-exo-(dimethylamino)isoborneol [(2S)-DAIB] exhibits unusual nonlinear phenomena. The enantiomeric purity of the product is much higher than that of the chiral source, DAIB, while the rate of the enantioselective catalysis decreases considerably as the enantiomeric excess (ee) of DAIB is lowered. Such effects originate from the reversible homochiral and heterochiral interaction of the coexistent enantiomeric zinc amino alkoxide catalysts which are formed from dimethylzinc and (2S)- and (2R)-DAIB. The thermodynamics of the five-component equilibration between the two monomers and three dimers, when coupled with the kinetics of the alkylation, strongly affects the extent of enantioselectivity and the reaction rate of the alkylation reaction. The overall profile of the nonlinear effects has been clarified mathematically using experimentally available parameters, viz., the equilibrium constants of the dimer/monomer conversion and the...
190 citations
176 citations
TL;DR: An iridium complex was found to be an efficient catalyst for allylic alkylation of allylic esters with a stabilized carbon nucleophile.
Abstract: An iridium complex was found to be an efficient catalyst for allylic alkylation of allylic esters with a stabilized carbon nucleophile. Highly regioselective alkylation at the substituted allylic t...
173 citations
TL;DR: In this article, the N,N-dimethyl derivative (R)-9 (MAP) was prepared via a sequence involving reductive alkylation with CH2O and NaBH4 (5 → 6), Pd(0)-catalyzed coupling of the corresponding triflate with Ph2P(O)H (7 → 8), and reduction of the resulting phosphine oxide with Cl3SiH (8 → 9).
Abstract: (R)-(+)-2-Amino-2‘-hydroxy-1,1‘-binaphthyl (NOBIN, 5) can be readily converted into a series of novel N,N-disubstituted aminophosphines 9 and 23−25. The N,N-dimethyl derivative (R)-9 (MAP) was prepared via a sequence involving reductive alkylation with CH2O and NaBH4 (5 → 6), Pd(0)-catalyzed coupling of the corresponding triflate with Ph2P(O)H (7 → 8), and reduction of the resulting phosphine oxide with Cl3SiH (8 → 9). Variation of this scheme was required for the preparation of 23−25 as the phosphinylation failed in the presence of bulky N substituents; the N-protected triflate 17 was first coupled with Ph2P(O)H, and the resulting phosphine oxide 18 was reduced with Cl3SiH to give the aminophosphine 19, which was then subjected to reductive alkylation with individual ketones and NaBH4. The new P,N-binaphthyls thus obtained (23−25 and 9) were utilized as chiral ligands in Pd(0)-catalyzed allylic substitution. The enantioselectivites obtained for racemic 1,3-diphenylprop-2-en-1-yl acetate (±)-26 and malona...
143 citations
TL;DR: N-Benzyl-N-(3-methyl-2-pyridyl)amine 1 reacts with various alkenes via sp3 C-H bond cleavage by catalytic Ru3(CO)12 to give the corresponding alkylated products.
139 citations
TL;DR: In this paper, a new method for producing unsymmetrical, tetrasubstituted ureas from N, N′-carbonyldiimidazole (CDI) is presented.
TL;DR: In this paper, a multistep process with participation of quarternary triazinylammonium salts 3−6 as the intermediates was found, with the rate of reaction strongly dependent on the structure of the tertiary amine.
Abstract: Activation of carboxylic function by means of 2-chloro-4,6-disubstituted-1,3,5-triazines 1 and 2 leading to triazine esters was found to be a multistep process with participation of quarternary triazinylammonium salts 3−6 as the intermediates, with the rate of reaction strongly dependent on the structure of the tertiary amine. The studies on alkylation of tertiary amines with CDMT revealed the two-step process AN + DN, and zwitterionic addition product 9 was identified by 1H NMR spectroscopy. Semiempirical modeling of the reaction as well as measured nitrogen and chlorine isotope effects also support this mechanism.
TL;DR: In this paper, the catalytic enantioselective alkylation of the benzophenone imine of glycine t-butyl ester is realized by an efficient homogeneous reaction with alkyl halides, the neutral, non-ionic phosphazene base (BEMP or BTPP), and chiral quaternary ammonium salts derived from thecinchona alkaloids.
TL;DR: In this article, the electrochemical properties of alkyl-terminated, (111)-oriented, n-type Si surfaces, prepared via a two-step halogenation/alkylation procedure, were analyzed in contact with CH3OH−1,1' -dimethylferrocene+/0 (Me2Fc+/ 0) solutions.
Abstract: The electrochemical properties of alkyl-terminated, (111)-oriented, n-type Si surfaces, prepared via a two-step halogenation/alkylation procedure, were analyzed in contact with CH3OH−1,1‘-dimethylferrocene+/0 (Me2Fc+/0) solutions. Current density−potential and differential capacitance−potential measurements of these surfaces in contact with CH3OH−Me2Fc+/0 indicated that the electrochemical properties of the alkyl-terminated surfaces were very similar to those of the H-terminated Si surface. The alkyl overlayers did not shift the Si band edges or induce significant surface recombination, but they did provide an additional electrical series resistance to charge transfer across the Si/liquid interface. The efficacy of alkyl overlayers in preventing photooxidation and photocorrosion of n-silicon surfaces was measured in contact with CH3OH−Me2Fc+/0 solutions to which a known amount of water had been added. Under these conditions, the alkyl-terminated surfaces consistently showed excellent current density−poten...
TL;DR: In this article, the authors investigated the performance of a CeO2-MgO catalysts for the alkylation of phenol with methanol and found that they had excellent selectivities to the sum ofo-cresol and 2,6-xylenol higher than 98%.
TL;DR: In this paper, high-yield reductive alkylation of (R)-(+)-1 and (R-(+))-2 has been achieved with a series of ketones (even as bulky as 2-adamantanone) and NaBH4/H2SO4 in THF at room temperature.
Abstract: High-yield reductive alkylation of (R)-(+)-1 and (R)-(+)-2 has been accomplished with a series of ketones (even as bulky as 2-adamantanone) and NaBH4/H2SO4 in THF at room temperature to give the re...
TL;DR: Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates.
Abstract: Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates. 1: R=Me, X=S; 2: R=H, X=C(CH3 )2 .
TL;DR: In this article, the benzenesulfonylation, acetylation, methylation and benzylation at the 1 position of indole and its derivatives with bases such as NaOH, KOH and NEt 3 are presented.
TL;DR: A new class of neutral mono-, and dicationic ruthenium(II) complexes containing a neutral terdentate donor system [C5H3N(CH2E)2-2,6] (E = PPh2 (PNP) or NMe2 (NN‘N)) has been found effective as catalyst precursor in N-(cyclo)alkylation reactions of aromatic amines with diols as mentioned in this paper.
Abstract: A new class of well-defined neutral mono-, and dicationic ruthenium(II) complexes containing a neutral terdentate donor system [C5H3N(CH2E)2-2,6] (E = PPh2 (PNP) or NMe2 (NN‘N)) has been found effective as catalyst precursor in N-(cyclo)alkylation reactions of aromatic amines with diols Y(CH2CH2OH)2 (Y = CH2, NR). With these catalysts, N-phenylpiperidine is synthesized from aniline and 1,5-pentanediol in 85% yield (at 180 °C for 24 h in 1,4-dioxane). With neutral RuCl2(NN‘N)(PPh3) as a catalyst precursor, aniline can be selectively N-monoalkylated with diols of the type HO(CH2)nOH (n = 4−6, 10) to give N-(n-hydroxyalkyl)anilines in 40−75% yield. To our knowledge, this represents the first useful catalytic route to this type of compounds. The new catalysts can also be used in the synthesis of arylpiperazines. For example, N-phenyl-N‘-methylpiperazine is obtained from aniline and MeN(CH2CH2OH)2 in yields up to 34%. N-[m-(Trifluoromethyl)phenyl]-N‘-methylpiperazine, TFMPMP, is successfully produced from m-(t...
TL;DR: The N-alkylated emeraldine bases are synthesized by incorporation of flexible alkyl chains onto the polyaniline (PAn) through an Nalkylation method.
TL;DR: In situ-infrared spectroscopy was used to study sorption and reaction of toluene and methanol over various basic catalysts (MgO, hydrotalcites, and basic zeolites) as discussed by the authors.
TL;DR: In this paper, a site-specific alkylation procedure for peptide amide functions is described, illustrated with an N-ethyl scan of Leu-enkephalin.
TL;DR: In this paper, supercritical 1-butene/isobutane alkylation is performed at temperatures lower than the critical temperature of isobutanes (<135 °C), resulting in virtually steady alkylate (trimethylpentanes and dimethylhexanes) production on both microporous zeolitic (H−USY) and mesoporous solid acid (sulfated zirconia) catalysts for experimental durations of up to nearly 2 days.
Abstract: Employing a molar excess of carbon dioxide (Pc = 71.8 bar; Tc = 31.1 °C), supercritical 1-butene/isobutane alkylation is performed at temperatures lower than the critical temperature of isobutane (<135 °C), resulting in virtually steady alkylate (trimethylpentanes and dimethylhexanes) production on both microporous zeolitic (H−USY) and mesoporous solid acid (sulfated zirconia) catalysts for experimental durations of up to nearly 2 days. At a space velocity of 0.25 g of 1-butene/g of catalyst/h, a feed CO2/isobutane/olefin ratio of 86:8:1, 50 °C, and 155 bar, roughly 5% alkylate yield (alkylates/C5+) and 20% butenes conversion are observed at steady state. The ability of the carbon dioxide based supercritical reaction mixtures to mitigate coking and thereby to maintain better pore accessibilities is also evident from the narrow product spectrum (confined to C8's), the lighter color of the spent catalyst samples, and relatively low surface-area and pore-volume losses (<25%) in the spent catalysts. For ident...
TL;DR: The utility of the alkylation of the imino functional group is extended to include diastereoand enantioselective variants that yield precursors for a number of pharmacologically active classes of compounds.
Abstract: The past few years have witnessed a profusion of highly efficient, catalytic, enantioand diastereoselective alkylations of carbonyl compounds.1 At the present time, the alkylation of the imino functional group presents a timely challenge in asymmetric catalysis, and recent work has focused on enol silanes, silyl ketene acetals, and TMSCN as carbon-based nucleophiles.2 We recently reported a means to alkylate R-imino ester 1 in up to 98% ee with enol silanes using chiral catalytic late-transition-metal phosphine complexes based on Ag(I), Cu(I), Ni(II), and Pd(II) (eq 1, R′ ) H).3 The best results were obtained with the easy-toprepare catalyst (R)-Tol-BINAP-CuClO4‚(MeCN)2. In this paper, we extend the utility of our reaction to include diastereoand enantioselective variants that yield precursors for a number of pharmacologically active classes of compounds.4 Regardless of the geometry of the enol silane, in many cases, excellent anti diastereoselectivity as well as enantioselectivity (up to 99% ee) can be obtained in the reaction (eq 1).5 In fact, the precise nature of the chiral phosphines we employ is responsible for the diastereoselectivity, as certain achiral bis(triphenylphosphine)-Cu(I) complexes lead to equal amounts of anti and syn products.
TL;DR: In this article, a ruthenium-catalyzed addition of terminal alkenes with terminal alkynes was proposed for the synthesis of a nanomolar fungal germination inhibitor, a 1,4-diene consisting of a terminal methylene and an (E)-1,2-disubstituted alkene.
Abstract: Alternaric acid, a nanomolar fungal germination inhibitor, is typified by a 1,4-diene, consisting of a terminal methylene and an (E)-1,2-disubstituted alkene. A new strategy for the synthesis of natural products containing such functionality stems from the development of a ruthenium-catalyzed addition of terminal alkenes with terminal alkynes. The alkyne substrate, 4-pentynoic acid, is commercially available or can be prepared in two steps by alkylation of tert-butyl acetate. The alkene substrate is prepared from commercially available (S)-2-methyl-1-butanol. This synthesis involves formation of a geometically defined trisubstituted alkene by involving Pd-catalyzed cross-coupling and asymmetric dihydroxylation. The ruthenium-catalyzed coupling proceeds best in the absence of alcohol protecting groups to maximize regioselectivity. The examples of this addition illustrated herein help elucidate some of the important factors controlling regioselectivity. They also illustrate the excellent chemoselectivity. T...
TL;DR: A chiral phosphonium salt has been synthesized as a novel phase-transfer catalyst, and used for asymmetric benzylation of t -butyl 2-oxocyclopentanecarboxylate to give the corresponding product with up to 50% ee as mentioned in this paper.
TL;DR: In this paper, the effect of positive charges on the polyamine moiety and the degree of unsaturation of the covalently attached lipid has been investigated using an ethidium bromide displacement assay.
TL;DR: Chiral phosphonium salts having two NH and two OH groups as hydrogen-bond donors have been synthesized as novel phase-transfer catalysts, and used for asymmetric alkylation of β-keto esters to give the corresponding products with up to 50% ee.
TL;DR: In this article, the effects of zeolite basicity, particle size, and pore dimensionality on the performance of side-chain alkylation with methanol were examined.