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Alkyl Bromides (alkyl + bromide)
Selected AbstractsChemInform Abstract: Silver-Catalyzed Benzylation and Allylation of Tertiary Alkyl Bromides with Organozinc Reagents.CHEMINFORM, Issue 42 2010Yukihiro Mitamura Abstract Silver salts catalyze the benzylation and allylation of tertiary alkyl bromides with organozinc reagents. [source] The First Palladium-Catalyzed Sonogashira Coupling of Unactivated Secondary Alkyl Bromides.CHEMINFORM, Issue 32 2006Gereon Altenhoff Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A Convenient One-Pot Negishi Coupling of Amino-Heteroaryl Chlorides and Alkyl Bromides.CHEMINFORM, Issue 17 2006Iain A. S. Walters Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Room-Temperature Stille Cross-Couplings of Alkenyltin Reagents and Functionalized Alkyl Bromides that Possess , Hydrogens.CHEMINFORM, Issue 32 2003Karsten Menzel Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A Convenient Method for the Alkylation of Sulfamides Using Alkyl Bromides and Mitsunobu Betaine.CHEMINFORM, Issue 18 2001Jean-Yves Winum Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] The Nonchiral Bislactim Diethoxy Ether as a Highly Stereo-Inducing Synthon for Sterically Hindered, , -Branched , -Amino Acids: A Practical, Large-Scale Route to an Intermediate of the Novel Renin Inhibitor AliskirenHELVETICA CHIMICA ACTA, Issue 8 2003Richard Göschke The diastereoselective synthesis of the sterically hindered, , -branched , -amino acid derivative (2S,4S)- 24a and its N -[(tert -butoxy)carbonyl](Boc)-protected alcohol (2S,4S)- 19, both key intermediates of a novel class of nonpeptide renin inhibitors such as aliskiren (1), is described. Initially, the analogous methyl ester (2S,4S)- 17 was obtained by alkylation of the chiral Schöllkopf dihydropyrazine (R)- 12a with the dialkoxy-substituted alkyl bromide (R)- 11a, which proceeded with explicitly high diastereofacial selectivity (ds ,98%) to give (2S,5R,2,S)- 13a (Scheme,4), followed by mild acid hydrolysis and N -Boc protection (Scheme,5). Conversely, the complete lack of stereocontrol and poor yields for the reaction of (R)- 11a with the enantiomeric (S)- 12b suggested, in addition to the anticipated shielding effect by the iPr group at C(2) of the auxiliary, steric repulsion between the MeOC(6) and the bulky residues of (R)- 11a in the proposed transition state, which would strongly disfavor both the Si and Re attack of the electrophile (see Fig.). Based on this rationale, alkylation of the readily accessible achiral diethoxy-dihydropyrazine 21 with (R)- 11a was found to provide a 95,:,5 mixture of diastereoisomers (2S,2,S)- 22a and (2R,2,S)- 23a in high yield (Scheme,6), which afforded in two steps and after recrystallization enantiomerically pure (2S,4S)- 24a. Similarly, the stereochemical course for the alkylation reactions of the related alkyl bromides (S)- 28a and (R)- 28b with both (R)- 12a and (S)- 12b as well as with the achiral 21 was investigated (Schemes,7,9). The precursor bromides (R)- 11a, (S)- 11b, (R)- 28a, and (S)- 28b were efficiently synthesized via the diastereoselective alkylation of the Evans 3-isovaleroyloxazolidin-2-ones (R)- 7a and (S)- 7b either with bromide 6 or with benzyl chloromethyl ether, and subsequent standard transformations (Schemes,3 and 7). A practical and economical protocol of the preparation of (2S,4S)- 24a on a multi-100-g scale is given. This is the first report of the application of an achiral dihydropyrazine, i.e., in form of 21, as a highly stereo-inducing synthon providing rapid access to a N -protected , -branched , -amino acid with (2S) absolute configuration. [source] Synthesis and characterization of alkylated N -vinylformamide monomers and their polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Lianjun Shi Abstract N -alkyl- N -vinylformamide monomers (alkyl: n -butyl, hexyl, decyl, and dodecyl) are synthesized in two steps: first, preparation of N -vinylformamide potassium salt by the reaction of N -vinylformamide (NVF) with potassium t -butoxide, then reaction with alkyl bromide. All four monomers are liquid and are characterized by IR, 1H NMR, 13C NMR, and mass spectra. They exist as rotomers in solution and a 2D NOE experiment on the N -hexyl containing polymer shows the E isomer to be favored. The polymerizability of the four monomers is from good to fair, depending upon the length of alkyl chain on the N -atom--the longer the chain length, the lower lower the polymerizability of monomer. The hydrolysis of poly(N -hexyl- N -vinylformamide) and poly(N -dodecyl- N -vinylformamide) under acidic and basic conditions was examined. Studies show that hydrolytic cleavage of formyl groups of poly (N -alkylated- N -vinylformamide) depends on the hydrophobicity of the alkyl substituent on the N -atom under acidic conditions; both polymers were hydrolyzed to only a minor extent under alkaline conditions. The N -alkylated monomers can copolymerize with NVF and demonstrate amphiphilic properties. The copolymers demonstrate a critical aggregation concentration above which they can solubilize a water insoluble dye; the N -hexyl containing copolymer stabilizes a castor oil-in-water emulsion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4994,5004, 2004 [source] Synthesis of 9,9-Dialkyl-4,5-diazafluorene Derivatives and Their Structure,Activity Relationships Toward Human Carcinoma Cell LinesCHEMMEDCHEM, Issue 4 2010Qiwei Wang Abstract A homologous set of 9,9-dialkyl-4,5-diazafluorene compounds were prepared by alkylation of 4,5-diazafluorene with the appropriate alkyl bromide and under basic conditions. The structures of these simple organic compounds were confirmed by spectroscopic techniques (FTIR, NMR, and FABMS). Their biological effects toward a panel of human carcinoma cells, including Hep3B hepatocellular carcinoma, MDAMB-231 breast carcinoma, and SKHep-1 hepatoma cells, were investigated; a structure,activity correlation was established with respect to the length of the alkyl chain and the fluorene ring structure. The relationship between the mean potency [log(1/IC50)] and alkyl chain length was systematically studied. The results show that compounds with butyl, hexyl, and octyl chains exhibit good growth inhibitory effects toward these three human carcinoma cell lines, and the 9,9-dihexyl-4,5-diazafluorene further exhibits antitumor activity in athymic nude mice Hep3B xenograft models. For the structurally related dialkylfluorenes that lack the diaza functionality, in,vitro cytotoxicity was not observed at clinically relevant concentrations. [source] Preferred Phosphorus Ylide Formation Upon Alkylation of Lithiobis(diphenylphosphanyl)acetonitrile,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2007Leonie Braun Abstract Deprotonation of the readily available chelate phosphane bis(diphenylphosphanyl)acetonitrile (6) leads to stabilized carbanion system 7. Lithiobis(diphenylphosphanyl)acetonitrile (7) features a unique thf-stabilized monomeric structure in the crystal form with a short cyanonitrogen,Li contact. Alkylation of 7 with n -alkyl bromides (R,Br, R = ethyl, n -propyl, n -butyl, n -hexyl) takes place selectively at one phosphorus atom to yield stabilized ylides 8a,d (two examples characterized by X-ray diffraction). Treatment of 7 with the more reactive alkylation agents methyl iodide or benzyl bromide results in alkylation at both phosphorus atoms to give delocalized bis(phosphonium)ylides 9a,b (both characterized by X-ray diffraction). Similarly, the reaction of 7 with 1,3-dibromopropane or 1,4-dibromobutane yields six- and seven-membered heterocyclic bis(phosphonium)ylides 10a,b, respectively. The spectroscopic characterization and X-ray crystal structure analysis again indicate the presence of delocalized Ph2RP,C(CN),PRPh2 substructures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Evaluation of S - and C(1) -Substituted Analogues of LincomycinHELVETICA CHIMICA ACTA, Issue 2 2009Marie-Pierre Collin Abstract New thioglycosides and C(1) -alkylated thioglycosides (S -ulosides) of lincomycin were synthesized, and their antibiotic activities were determined. The S -aryl and S -arylalkyl analogues 11a,11i were obtained by S -glycosylation of the sulfoxides 7 with arenethiols, or by S -alkylation of the thiol 14 with alkyl bromides. Lincomycin derivatives 27, 32a, 32b, 38a, 38b, 44, and 47 were prepared via Henry reaction or Michael addition of the lincosamine-derived 1-deoxy-1-nitropyranoses 22. The S -alkyl derivatives showed a similar activity and specificity as lincomycin. Lipophilic S -uloside analogues were two- to fourfold less active than the parent antibiotic, whilst the hydrophilic analogues were inactive. [source] The Nonchiral Bislactim Diethoxy Ether as a Highly Stereo-Inducing Synthon for Sterically Hindered, , -Branched , -Amino Acids: A Practical, Large-Scale Route to an Intermediate of the Novel Renin Inhibitor AliskirenHELVETICA CHIMICA ACTA, Issue 8 2003Richard Göschke The diastereoselective synthesis of the sterically hindered, , -branched , -amino acid derivative (2S,4S)- 24a and its N -[(tert -butoxy)carbonyl](Boc)-protected alcohol (2S,4S)- 19, both key intermediates of a novel class of nonpeptide renin inhibitors such as aliskiren (1), is described. Initially, the analogous methyl ester (2S,4S)- 17 was obtained by alkylation of the chiral Schöllkopf dihydropyrazine (R)- 12a with the dialkoxy-substituted alkyl bromide (R)- 11a, which proceeded with explicitly high diastereofacial selectivity (ds ,98%) to give (2S,5R,2,S)- 13a (Scheme,4), followed by mild acid hydrolysis and N -Boc protection (Scheme,5). Conversely, the complete lack of stereocontrol and poor yields for the reaction of (R)- 11a with the enantiomeric (S)- 12b suggested, in addition to the anticipated shielding effect by the iPr group at C(2) of the auxiliary, steric repulsion between the MeOC(6) and the bulky residues of (R)- 11a in the proposed transition state, which would strongly disfavor both the Si and Re attack of the electrophile (see Fig.). Based on this rationale, alkylation of the readily accessible achiral diethoxy-dihydropyrazine 21 with (R)- 11a was found to provide a 95,:,5 mixture of diastereoisomers (2S,2,S)- 22a and (2R,2,S)- 23a in high yield (Scheme,6), which afforded in two steps and after recrystallization enantiomerically pure (2S,4S)- 24a. Similarly, the stereochemical course for the alkylation reactions of the related alkyl bromides (S)- 28a and (R)- 28b with both (R)- 12a and (S)- 12b as well as with the achiral 21 was investigated (Schemes,7,9). The precursor bromides (R)- 11a, (S)- 11b, (R)- 28a, and (S)- 28b were efficiently synthesized via the diastereoselective alkylation of the Evans 3-isovaleroyloxazolidin-2-ones (R)- 7a and (S)- 7b either with bromide 6 or with benzyl chloromethyl ether, and subsequent standard transformations (Schemes,3 and 7). A practical and economical protocol of the preparation of (2S,4S)- 24a on a multi-100-g scale is given. This is the first report of the application of an achiral dihydropyrazine, i.e., in form of 21, as a highly stereo-inducing synthon providing rapid access to a N -protected , -branched , -amino acid with (2S) absolute configuration. [source] Eco-friendly methodologies for the synthesis of some aromatic esters, well-known cosmetic ingredientsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2005C. Villa Synopsis Solid,liquid solvent-free phase transfer catalysis (PTC) and acidic catalysis in dry media were applied, with noticeable improvement and simplification over classical procedures in a Green Chemistry context, to the synthesis of some aromatic esters useful as cosmetic ingredients: 3-methylbutyl 4-methoxycinnamate, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 4-(dimethylamino)benzoate and 2-ethylhexyl salicylate, well-known ultraviolet B sunscreen filters; 4-isopropylbenzyl salicylate, UV absorber and cutaneous antilipoperoxidant; propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate (parabens), antimicrobial agents. The reactions were performed under microwave (MW) activation and conventional heating. The best results for the synthesis of cinnamic, salicylic and 4-(dimethylamino)benzoic esters were achieved by in situ preformed carboxylates alkylation with alkyl bromides using PTC. The 4-hydroxybenzoates were obtained in good yields by classical esterification of the acid with alcohols using a simple heterogeneous mixture of reagents with catalytic amounts of p -toluenesulfonic acid (PTSA). The comparisons of yields and thermal profiles under either MW or conventional heating were studied and reported. Résumé La catalyse par transfert de phase (CTP) solide-liquide sans solvant et l'estérification acido-catalysée en ,,milieu sec'' ont été appliquées, dans le cadre de la ,,chimie verte'', avec des nettes améliorations et simplifications par rapport aux méthodes classiques, à la synthèse de certains esters aromatiques, ingrédients cosmétiques: 3-methylbutyl 4-méthoxycinnamate, 2-éthylhéxyl 4-méthoxycinnamate, 2-éthylhéxyl 4-(diméthylamino) benzoate et 2-éthylhéxyl salicylate, filtres solaires UVB bien connus; 4-isopropylbenzyl salicylate, filtre UV et antilipopéroxydant cutané; propyl 4-hydroxybenzoate et butyl 4-hydroxybenzoate (parabens), agents antimicrobien. Les réactions ont été procédées sous irradiation micro-onde et par chauffage classique. Pour la synthèse des esters dérivés de l'acide cinnamique, salicylique et 4-(diméthylamino)benzoïque les meilleurs résultats ont été obtenus grâce à la CTP par alkylation des carboxylates (préformés in situ) avec des bromures d'alkyle. Les esters de l'acide 4-hydroxybenzoique ont été obtenus avec de bons rendements par simple mélange hétérogène des réactifs et d'acide p-toluènesulfonique (PTSA) comme catalyseur. Les rendements et les profils de montée en température sous micro-ondes et par chauffage classique ont été comparés. [source] One-Pot Thioetherification of Aryl Halides Using Thiourea and Alkyl Bromides Catalyzed by Copper(I) Iodide Free from Foul-Smelling Thiols in Wet Polyethylene Glycol (PEG 200)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Habib Firouzabadi Abstract In this article, we have developed a new protocol for the thioarylation of structurally diverse alkyl bromides such as benzyl, cinnamyl, n -octyl, cyclohexyl, cyclopentyl, and tert -butyl bromides with aryl iodides, bromides and an activated chloride using thiourea catalyzed by copper(I) iodide in wet polyethylene glycol (PEG 200) as an eco-friendly medium in the presence of potassium carbonate at 80 and 100,°C under an inert atmosphere. The process is free from foul-smelling thiols which makes this method more practical for the thioetherification of aryl halides. Another important feature of this method is the variety of alkyl bromides which are commercially available for the in situ generation of thiolate ions with respect to the existing protocols in which the less commercially available thiols are directly used for the preparation of arylthio ethers. [source] Regioselective Palladium(0)-Catalyzed Cross-Coupling Reactions and Metal-Halide Exchange Reactions of Tetrabromothiophene: Optimization, Scope and LimitationsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009ng Thanh Tùng Abstract The Suzuki reaction of tetrabromothiophene with arylboronic acids provides a regioselective approach to various 5-aryl-2,3,4-tribromothiophenes, symmetrical 2,5-diaryl-3,4-dibromothiophenes, and tetraarylthiophenes. Unsymmetrical 2,5-diaryl-3,4-dibromothiophenes are prepared by Suzuki reaction of 5-aryl-2,3,4-tribromothiophenes. Tetraarylthiophenes containing two different types of aryl groups are obtained by Suzuki reactions of 2,5-diaryl-3,4-dibromothiophenes. During the optimization of the conditions of each individual reaction, the solvent, the catalyst and the temperature play an important role. In several cases, classical conditions [use of tetrakis(triphenylphosphane)palladium(0), Pd(PPh3)4, as the catalyst] gave excellent yields. The yields of those transformations which failed or proceeded sluggishly could be significantly improved by application of a new biarylmonophosphine ligand developed by Buchwald and co-workers. Regioselective metal-halide exchange reactions of tetrabromothiophene provide a convenient approach to various 2,5-disubstituted 3,4-dibromothiophenes. 5-Alkyl-2-trimethylsilyl-3,4-dibromothiophenes could be prepared in one pot by sequential addition of trimethylchlorosilane and alkyl bromides. The reaction of tetrabromothiophene with methyl chloroformate and subsequent Suzuki reactions afforded 3,4-diaryl-2,5-bis(methoxycarbonyl)thiophenes. [source] Cyclometalated 2-phenylpyridine complex [RuII(o -C6H4 -py)(MeCN)4]PF6 as a tunable catalyst for living radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008F. Diaz Camacho Abstract The cyclometalated complex [RuII(o -C6H4 -py)(MeCN)4]PF6 (1) with a ,-RuC bond and four substitutionally labile acetonitrile ligands mediates radical polymerization of different vinyl monomers, viz. n -butyl acrylate, methyl methacrylate, and styrene, initiated by three alkyl bromides: ethyl 2-bromoisobutyrate, methyl 2-bromopropionate, and 1-phenylethyl bromide. The polymerization requires the presence of Al(OiPr)3 and occurs uncontrollably as a conventional radical process. The variation of the molar ratio of the components of the reaction mixture, such as initiator, Al(OiPr)3 and catalyst, affected the polymerization rates and the molecular weights but did not improve the control. A certain level of control has been achieved by adding 0.5 eq of SnCl2 as a reducing agent. Tin(II) chloride decreased the rate of polymerization and simultaneously the molecular weights became conversion-dependent and the polydispersities were also narrowed. Remarkably, the level of control was radically improved in the presence of excess of the poorly soluble catalyst (1), when the added amount of (1) was not soluble any more, i.e., under heterogeneous conditions, the system became adjustable and the living polymerization of all three monomers was finally achieved. Possible mechanisms of the (1)-catalyzed polymerization are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4193,4204, 2008 [source] ChemInform Abstract: Silver-Catalyzed Benzylation and Allylation of Tertiary Alkyl Bromides with Organozinc Reagents.CHEMINFORM, Issue 42 2010Yukihiro Mitamura Abstract Silver salts catalyze the benzylation and allylation of tertiary alkyl bromides with organozinc reagents. [source] | ||||||||||