Showing papers on "Grignard reaction published in 2005"
TL;DR: The Grignard metathesis (GRIM) polymerization of 3-alkylthiophenes proceeds by a quasi-living chain growth mechanism, not by a step growth process as mentioned in this paper.
Abstract: The Grignard metathesis (GRIM) polymerization of 3-alkylthiophenes proceeds by a quasi-“living” chain growth mechanism, not by a step growth process. Kinetic studies of the Grignard metathesis polymerization of 2,5-dibromo-3-alkylthiophenes showed that the molecular weight of poly(3-alkylthiophenes) is a function of the molar ratio of the monomer to nickel initiator, and conducting polymers with predetermined molecular weights and relatively narrow molecular weight distributions (PDIs = 1.2−1.5) can be made. Sequential monomer addition resulted in new block copolymers containing different poly(3-alkylthiophene) segments.
602 citations
TL;DR: Using a modified Grignard metathesis (GRIM) reaction, a series of polymers have been synthesized bearing functional groups on one or both ends of the polymer as mentioned in this paper.
Abstract: A simple method for the synthesis of end-functionalized regioregular poly(3-alkylthiophene)s is presented. Using a modified Grignard metathesis (GRIM) reaction, a series of polymers have been synthesized bearing functional groups on one or both ends of the polymer. This method has been demonstrated to work with a variety of different types of Grignard reagents (i.e., aryl, alkyl, allyl, vinyl, etc.). The reactivity of these depends on their nature, where allyl, ethynyl, and vinyl groups produced monofunctionalized polymers, and all others yielded difunctionalized polymers. The end group composition of the polymers was monitored by a combination of MALDI-TOF and 1H NMR and approaches 100% in most cases. By utilizing the proper protecting groups −OH, −CHO, and −NH2 groups have been incorporated onto the polymer ends. The main advantage of this method is that it allows for the in situ functionalization of regioregular polythiophene, generating a variety of end-capped polymers in one step. This approach is ad...
353 citations
206 citations
132 citations
TL;DR: In this paper, a new procedure was developed for the synthesis of 3-ethylquinoxalin-2(1H)-one from o-phenylenediamine and ethyl 2-oxobutanoate.
Abstract: A new and effective procedure was developed for the synthesis of 3-ethylquinoxalin-2(1H)-one from o-phenylenediamine and ethyl 2-oxobutanoate. The latter was prepared by the Grignard reaction of diethyl oxalate with ethylmagnesium bromide or iodide. The ethyl group in 3-ethylquinoxalin-2(1H)-one can readily be converted into various functional groups: α-bromoethyl, α-thiocyanato, α-azidoethyl, α-phenylaminoethyl, acetyl, and bromoacetyl. The reaction of 3-(bromoacetyl)quinoxalin-2(1H)-one with thiourea and hydrazine-1,2-dicarbothioamide gives the corresponding 3-(2-amino-4-thiazolyl) derivatives.
33 citations
TL;DR: In this article, a chemoenzymatic method for the asymmetric total synthesis of d-biotin starting from the commercially available cis-1,3-dibenzyl-2-imidazolidone-4,5-dicarboxylic acid has been developed.
Abstract: A practical chemoenzymatic method for the asymmetric total synthesis of d-biotin (1) starting from the commercially available cis-1,3-dibenzyl-2-imidazolidone-4,5-dicarboxylic acid (2) has been developed. The key step of the synthesis is the highly enantioselective hydrolysis of meso-dicarboxylic esters by a polymer-supported pig liver esterase and introduction of a formyl group at the C-4 position in 4 via a Grignard reaction. The polymer-supported PLE can be recovered quantitatively from the reaction mixture by simple filtration and reused without significant loss of activity.
27 citations
TL;DR: In this article, an enantio-and stereocontrolled total synthesis of (+)-boronolide from valeraldehyde is described, where the key steps include a Sharpless asymmetric dihydroxylation, a chelation controlled Grignard reaction, and a ring closing metathesis.
26 citations
TL;DR: In this paper, a series of 3,3′-diaryl biindenylidenedione derivatives were synthesized through Grignard reaction and the absolute configurations of the stereoisomers were determined by single crystal X-ray crystallography.
20 citations
TL;DR: In this article, an efficient approach to enantiomerically pure (+)-deacetylanisomycin 2a and a formal synthesis of (+)-anisomcin 2 (11% overall yield in 10 steps) have been achieved through simple and good yielding reactions, starting from 1,2:3,4:5,6-tri-O-isopropylidene- d -mannitol 3.
Abstract: An efficient approach to enantiomerically pure (+)-deacetylanisomycin 2a and a formal synthesis of (+)-anisomycin 2 (11% overall yield in 10 steps) have been achieved through simple and good yielding reactions, starting from 1,2:3,4:5,6-tri-O-isopropylidene- d -mannitol 3. Grignard reaction and intramolecular cyclisation reactions are key steps in the strategy.
20 citations
TL;DR: In this article, two seco-theaspiranes with pronounced blackcurrant notes were synthesized by a synthetic sequence consisting of Grignard reaction, Lindlar hydrogenation, and cyclization followed by optional Pd-catalyzed hydrogenation.
Abstract: Two seco-theaspiranes with pronounced blackcurrant notes, 2-tert-butyl-5-methyl-2-propyl-2,5-dihydrofuran (7) and 2-tert-butyl-5-methyl-2-propyltetrahydrofuran (8), were synthesized by a synthetic sequence consisting of Grignard reaction, Lindlar hydrogenation, and cyclization followed by optional Pd-catalyzed hydrogenation. The sequence was modified for the synthesis of the oxygenated analogs 2-(2'-tert-butyl-5'-methyltetrahydrofuran-2'-yl)propan-2-ol (9) and 3-(2'-tert-butyl-5'-methyltetrahydrofuran-2'-yl)butan-2-one (10). The first modification featured trimethylsilyl ether protection and stepwise construction of the alkyne moiety necessitated by steric hindrance. In the second modification, a but-2-en-2-yl group was utilized as latent 3-hydroxybut-1-en-2-yl functionality, and the steric constraint around the tertiary hydroxy group was exploited to introduce a stereocenter by S N 2 ring closure. As for the parent compounds 7 and 9. the odor of the oxygenated secotheaspiranes was shifted towards a woody tonality. The like-diastereomer 9a even had a typical patchouli profile, and the enantiomers 10a and 10b differed significantly in their olfactory properties.
17 citations
TL;DR: A direct and highly stereoselective (E)-4-benzyloxybut-2-enylation of aldehydes was successfully carried out to give 5-benZyloxyhomoallylic alcohol via an allyl-transfer reaction using a chiral allyl donor.
TL;DR: In this article, the asymmetric synthesis of cis -1,4-amino alcohols with a norbornene backbone was performed starting with (2 S,3 R )-(−)- cis -hemiester 2 (98% ee).
Abstract: The asymmetric synthesis of cis -1,4-amino alcohols with a norbornene backbone was performed starting with (2 S ,3 R )-(−)- cis -hemiester 2 (98% ee). Chemoselective amination with NH 4 OH and HMPTA followed by LAH reduction afforded 5 and 7 , respectively. Amido ester 6 was transformed into chiral ligand 9 with Grignard reaction followed by LAH reduction. The chiral ligands 5 , 7 , and 9 were subjected to asymmetric diethylzinc addition to examine their effectiveness as chiral catalysts. Among these, chiral ligand 7 exhibited the highest enantioselectivity (88% ee).
TL;DR: The Grignard reaction of 2,4,6-tri(tert-butyl)phenylmagnesium bromide with zinc dichloride in THF yields monomeric bis[2.4, 6-tri[tert]-phenyl]zinc (1) as mentioned in this paper.
Abstract: The Grignard reaction of 2,4,6-tri(tert-butyl)phenylmagnesium bromide with zinc dichloride in THF yields monomeric bis[2,4,6-tri(tert-butyl)phenyl]zinc (1). Due to the steric demand of the tert-butyl groups 1 has a bent CZnC moiety and the boat-shaped aryl groups are in a staggered conformation. After the transmetallation of 1 with cesium in a solvent mixture of 1,2-dimethoxyethane (DME) and toluene (1,2-dimethoxyethane-O,O′)cesium [2,4,6-tri(tert-butyl)phenolate] (2) is isolated. A polymeric structure is formed in the crystalline state by linkage of these molecules via a Cs-O bond of the phenolate oxygen atoms and a η6-coordination of the aryl moiety of another molecule to the cesium cations. Furthermore, in the solid state the cesium cation completes his coordination sphere by bonds to a bidentate ether molecule and by close contacts to a tert-butyl group of a neighboring molecule.
TL;DR: The bis(arylene silanes) p,p‘-HMe2SiC6H4EMe2C 6H4SiMe2H (E = C (10), Si (11), Ge (12), Sn(13)) were prepared by the in situ Grignard reaction of p, p‘ -BrC6h4CMe2CMe 2C6 h4Br, Mg turnings, and HSiMe2Cl (for...
TL;DR: In this article, an enantioselective synthesis of (+)-biotin starting from naturally available cysteine is described, and the key steps are the unusual stereochemical outcome of radical cyclization of compound 10 to prepare 5,5-fused system 11, and the introduction of C4-sidechain at C 6 in 13 via a Grignard reaction.
TL;DR: In this paper, the authors studied the reaction of the aryl radical clock 1-bromo-2-(3-butenyl)benzene towards potassium and magnesium in the presence and absence of various additives, at ambient and low temperatures.
TL;DR: In this paper, the formation of phenylmagnesium chloride and bromide in toluene in the presence of one or two equivalents of diethyl ether or THF were investigated kinetically.
TL;DR: In this article, the unexpected occurrence of ketones 9 and 16 in addition to expected alcohols 5 and 15 in the synthesis of sesquiterpenes salsolenketone 1 and salsolene oxide 2 during Grignard reactions of the corresponding aldehydes with bromoalkenes under air and water free conditions by the Meerwein-Ponndorf-Verley-Oppenauer reaction is reported.
01 Sep 2005
TL;DR: Among compounds tested, cytosine derivative 15a was found to show high growth inhibition against a broad range of human tumor cell lines.
Abstract: Novel pyrimidine nucleosides with fluorocyclopentene ring were synthesized from D-ribose via stereoselective Grignard reaction and electrophilic vinyl fluorination as key steps. Among compounds tested, cytosine derivative 15a was found to show high growth inhibition against a broad range of human tumor cell lines.
TL;DR: The adenine analogue 12 exhibited moderate antiviral activity against the HCMV, and a new stereoselective synthesis of 6′‐branched Carbovir analogues was accomplished in this study.
Abstract: A new stereoselective synthesis of 6'-branched Carbovir analogues was accomplished in this study. The introduction of a methyl group in the requisite 6'(alpha)-position was carried out using an ester enolate alkylation (LHMDS, CH3I). The desired cyclopentenol 7 was synthesized via a Felkin-Anh-controlled Grignard addition and ring-closing metathesis using second-generation Grubbs' catalyst. The natural bases (adenine, cytosine) were efficiently coupled using a Pd(0) catalyst. When the synthesized compounds were examined for their activity against several viruses such as the HIV-1, HSV-1, HSV-2, and HCMV, the adenine analogue 12 exhibited moderate antiviral activity against the HCMV.
TL;DR: In this article, a 4-bromo-2,3-dimethoxybutyl(phenyl)phosphinate (10a) was prepared from 2,3di-O-methyl-L-threitol (12) in five steps.
Abstract: Ethyl 4-bromo-2,3-dimethoxybutyl(phenyl)phosphinate (10a) was prepared from 2,3-di-O-methyl-L-threitol (12) in five steps. Reduction of 10a with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by the action of hydrogen peroxide, afforded 3,4-dimethoxy-l-phenylphospholane 1-oxide (3), while the reaction of 10a with magnesium in boiling THF resulted in the formation of ethyl 2-methoxy-3-butenyl(phenyl)phosphinate (26).
Patent•
09 Feb 2005
TL;DR: In this article, a Grignard reaction with 3-bromoanisole in a suitable solvent and in the presence of an inorganic lithium salt and an α,ω-dialkoxyalkane was proposed.
Abstract: A process for preparing 2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol with high stereoselectivity and high yield by reacting 2-[(dimethylamino)methyl]-cyclohexanone in a Grignard reaction with a Grignard compound of 3-bromoanisole in a suitable solvent and in the presence of an inorganic lithium salt and an α,ω-dialkoxyalkane.
TL;DR: Efficient Pauson-Khand reactions on quinolines bearing 1-en-7-ynes features gave tetrahydrocyclopenta[c]acridine derivatives that provides new acridine structures in four high yielding steps from commercially available quinoline intermediates.
Abstract: Efficient Pauson-Khand reactions on quinolines bearing 1-en-7-ynes features gave tetrahydrocyclopenta[c]acridine derivatives. The quinoline intermediates were obtained in two steps: a Sonogashira reaction with functionalized alkynes (TMS, Bu, Ph, CHB 2 OTHP) followed by a Grignard reaction with allylmagnesium bromide. The sequence provides new acridine structures in four high yielding steps from commercially available quinolines.
TL;DR: In this article, the vinyl group of MPPa was converted into alkyl carbonyl group by Grignard reaction and oxidization to give chlorins 2, 3 and 5.
Abstract: From methyl pyropheophorbide-a (MPPa, 1), the vinyl group of methyl pyropheophorbide-a was converted into alkylcarbonyl group by Grignard reaction and oxidization to give chlorins 2, 3 and 5. The Vilsmeier reaction of nickel 3-substituent-3-devinylpyropheophorbide-a (6), which was prepared by the metallation with nickel acetate, with 3-dimethylamino-acrolein/phosphoryl chloride (3-DMA/POCl3) was carried out to give δ-meso-formylvinyl-pyropheophorbide-a (7) in good yield. The benzoisobacterichlorin (8) was obtained by the treatment of 7b with concentrated sulfuric acid.
TL;DR: The stereochemistry of the addition of methylmagnesium bromide to a steroidal 4,5-epoxy-3-ketone and the epoxidation to the corresponding 3-alkyl- 3-hydroxy-4-enes by per-acid was determined by the stereochemical of the allylic alcohol.
Patent•
31 Aug 2005
TL;DR: A process for synthesizing 2-trifluoromethyl indole from O-tolyamine is described in this paper, which includes preparing 2,2,2 trifluoro-N-Otolylimine acylchloride and Grignard reaction to obtain target product.
Abstract: A process for synthesizing 2-trifluoromethyl indole from O-tolyamine includes preparing 2,2,2-trifluoro-N-O-tolylimine acylchloride, reacting on free radical to obtain 2,2,2-trifluoro-N-(O-bromomethylphenyl) iminoacyl chloride, and Grignard reaction to obtain target product.
TL;DR: In this paper, the Grignard reaction of 4-fluoro-[2,3,5,6-2H4]bromobenzene and pyridine-4-aldehyde followed by consecutive deoxygenation and heteroatomic ring saturation in the presence of palladium on carbon catalyst is described.
Abstract: Pure 4-(4-fluoro-[2,3,5,6-2H4]benzyl)piperidine was prepared via the Grignard reaction of 4-fluoro-[2,3,5,6-2H4]bromobenzene and pyridine-4-aldehyde followed by consecutive deoxygenation and heteroatomic ring saturation in the presence of palladium on carbon catalyst. An improved method for the catalytic H/D exchange in benzylic positions of 4-(4-fluorobenzyl)piperidine and its d4 derivative has also been described. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: The Grignard reaction shows high degree of stereoselectivity according with Cram rule as mentioned in this paper, and the crystal structure of 4 indicates that dihydrofuran ring was opened to form a phenolic hydroxyl group and a three-membered ring structure.
Abstract: The reaction of 7α-acetyl-6,14-endoethano-6,7,8,14-tetrahydrothebaine with 2-(thien-2-yl)ethylmagnesium bromide was investigated. The tertiary alcohol derivative 7α-[R-1-hydroxyl-1-methyl-3-(thien-2-yl)propyl])-6,14-endoethano-6,7,8,14-tetrahydrothebaine (3) and a by-product 4 were isolated. The structure of 4 was elucidated by X-ray analysis. The Grignard reaction shows high degree of stereoselectivity according with Cram rule. The crystal structure of 4 indicates that dihydrofuran ring was opened to form a phenolic hydroxyl group and a three-membered ring structure. It maintains the main rigid structure of morphine and contains a C(6)-C(14) enthano bridge. The 1-hydroxyl-1-methyl-3-(thien-2-yl)propyl group at C(7) position adopted S-configuration.
Journal Article•
TL;DR: In this paper, the diastereoselectivity of various Grignard reagents to N-pyruvoyl- (3) and N-phenylglyoxyloxyloyl-(2R)-bomane-10,2-sultam (4) under thermal and Lewis-acid catalytic conditions are studied.
Abstract: Additions of various Grignard reagents to N-pyruvoyl- (3) and N-phenylglyoxyloyl-(2R)-bomane-10,2-sultam (4) under thermal and Lewis-acid catalytic conditions are studied. High diastereoselectivity was observed in these reactions, and in the case of vinylmagnesium bromide additions to α-ketoimide 4 a change of direction of asymmetric induction was found.
TL;DR: In this paper, a new procedure was developed for the synthesis of 3-ethylquinoxalin-2(1H)-one from o-phenylenediamine and ethyl 2-oxobutanoate.
Abstract: A new and effective procedure was developed for the synthesis of 3-ethylquinoxalin-2(1H)-one from o-phenylenediamine and ethyl 2-oxobutanoate. The latter was prepared by the Grignard reaction of diethyl oxalate with ethylmagnesium bromide or iodide. The ethyl group in 3-ethylquinoxalin-2(1H)-one can readily be converted into various functional groups: α-bromoethyl, α-thiocyanato, α-azidoethyl, α-phenylaminoethyl, acetyl, and bromoacetyl. The reaction of 3-(bromoacetyl)quinoxalin-2(1H)-one with thiourea and hydrazine-1,2-dicarbothioamide gives the corresponding 3-(2-amino-4-thiazolyl) derivatives.