Showing papers on "Grignard reaction published in 1991"
154 citations
76 citations
TL;DR: In this paper, an efficient approach has been developed to construct the entire TOP-HALF of FK-506 involving Grignard reaction of a C-29 bromide with a C -27 methylketo fragment.
54 citations
TL;DR: Theoretical calculations using self-consistent field (SCF) and Moller-Plessett perturbation theory, up to fourth order (MP4), have been carried out on the gas-phase Mg+CH 3 X→CH 3 MgX Grignard reaction surface for X=F and Cl as discussed by the authors.
Abstract: Theoretical calculations using self-consistent field (SCF) and Moller-Plessett perturbation theory, up to fourth order (MP4), have been carried out on the gas-phase Mg+CH 3 X→CH 3 MgX Grignard reaction surface for X=F and Cl. The transition-state energies, geometries, and vibrational frequencies for both reactions are presented and compared to the smaller Mg+HX→HMgX reaction. The transition states for both X=F and X=Cl are found to process C s symmetry and to be almost identical in structure. The activation energy for the Mg + fluoromethane reaction is found to be 31.2 kcal-mol −1 , while that for the chloromethane reaction is substantially higher, at 39.4 kcal.mol −1 , calculated at the MP4SDTQ level by using the 6-311G(d,p) basis. The intrinsic reaction coordinate has been followed down from the transition state toward both reactants and product for the Mg + CH 3 F→CH 3 MgF reaction, confirming the connection of these points on the potential surface
51 citations
TL;DR: In this article, the selective functionalization of 2,2'-bithiophene molecule was described, which was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5, 5' positions.
Abstract: The selective functionalization of the 2,2'-bithiophene molecule is described. Selective alkyl substitution at the 3,3' positions was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5,5' positions. The resultant 3,3'-dibromo-2,2'-bithiophene was transformed via a Grignard reaction to give a series of 3,3'-dialkyl-2,2'-bithiophenes. Finally, nitration of the active 5,5' positons gave the corresponding 3,3'-dialkyl-5,5'-dinitro-2,2'-bithiophenes
49 citations
TL;DR: In this article, a cyano group in 1, 2, 4, 5 triaznes, regardless of its position, acted as an effective leaving group in reactions with carbanions.
Abstract: A cyano group in 1, 2, 4-triaznes, regardless of its position, acted as an effective leaving group in reactions with carbanions. Thus, the reactions gave the corresponding substituted products in place of the compounds formed by addition reaction of carbanions to the cyano group. Grignard reaction of these carbonitriles is also described.
35 citations
TL;DR: In this article, the benzotriazole residues in both the primary products and in their substituted derivatives can be displaced by the alkyl anions of Grignard reagents or by hydride ions allowing the elaboration of new types of substituted phenols.
Abstract: Phenols and naphthols are benzotriazolylmethylated by 1-(hydroxymethyl)-1H-benzotriazole (13) (a formaldehyde derivative) in the o- or (if both o-positions are occupied) in the p-position. The reaction can be extended to other aldehydes in the case of the naphthols. The methylene group in the o-(benzotriazolylmethyl)phenols can be lithiated (but only after trimethylsilyl protection of the hydroxy group) and then substituted by various electrophiles. The benzotriazole residues in both the primary products and in their substituted derivatives can be displaced by the alkyl anions of Grignard reagents or by hydride ions allowing the elaboration of many new types of substituted phenols.
33 citations
TL;DR: In this paper, the preparation of novel 2-(arylsulfonyl)vinamidinium salts is described, along with the reactions of these materials with amidines, hydrazine, hydroxylamine, and Grignard Reagents.
Abstract: The preparation of novel 2-(arylsulfonyl)vinamidinium salts is described. The reactions of these materials with amidines, hydrazine, hydroxylamine, sodium borohydride, and Grignard Reagents are presented along with an evaluation of their chemical behavior as compared to the 2-arylvinamidinium salts
32 citations
23 citations
TL;DR: A wide variety of soluble and fusible derivatives of poly(1,4-phenylenevinylene) were prepared by the Pd-catalysed arylation of ethylene with dihalogenoarenes as discussed by the authors.
21 citations
TL;DR: In this article, the methylene groups in the products are readily substituted by electrophiles via the lithiated derivatives via the substitution of the benzotriazole group can be effected by organometallic reagents or by electron-rich benzoid compounds to afford a versatile method for the synthesis of substituted aryl ethers.
Abstract: Methoxybenzenes and -naphthalenes are benzotriazolylmethylated in the para-position or if this is blocked in an ortho- position. The methylene groups in the products are readily substituted by electrophiles via the lithiated derivatives. Displacement of the benzotriazole group can be effected by organometallic reagents or by electron-rich benzoid compounds to afford a versatile method for the synthesis of substituted aryl ethers.
TL;DR: In this article, the reaction of carbonyl compounds with α-lithio- or α-halozinc N-methoxy-N-methylamides, followed by silylation and Grignard addition resulted in a regiocontrolled synthesis of β-trimethylsilyloxy carbonyls compounds.
TL;DR: In this article, the authors compared addition (Add.) vs reduction (Red.) products in the reactions of substituted benzophenones, acetophenone and fluorenone with "EtMgBr" in diethyl ether, 1,2-dimethoxyethane and tetrahydrofuran.
TL;DR: In this paper, the synthesis and transformation of unsaturated organomagnesium compounds obtained from 1,3-dienes by nontraditional methods is discussed. But the results of these methods are limited.
TL;DR: In this article, the ene reaction of trifluoroacetaldehyde with various ene compounds as a good enophile in the presence of Lewis acids, among which methylaluminum dichloride workded best, though polymerization of the aldehyde caused by the Lewis acid often lowered the isolation yields of the reaction.
Abstract: As an extension of our studies on the ene reaction of trifluoromethyl ketones, the ene reaction of trifluoroacetaldehyde was examined. The aldehyde reacted with various ene compounds as a good enophile in the presence of Lewis acids, among which methylaluminum dichloride workded best, though polymerization of the aldehyde caused by the Lewis acid among which methylaluminum dichloride worked best, though polymerization of the aldehyde caused by the Lewis acid often lowered the isolation yields of the ene reaction. The ene reaction products were successfully oxidized to trifluoromethyl β, γ-unsaturated ketones with Dess Martin reagent. Reduction of the ene reaction products followed by oxidation with Jones reagent gave saturated trifluoromethyl ketones. The β, γ-unsaturated ketone rearranged on thermolysis to an α, β-unsaturated ketone. These ketones obtained were converted to otehr types of trifluoromethyl compounds. Thus, the ene reaction of trifluoroacetaldehyde provides a versatile method for synthesis of many types of trifluoromethyl compounds. During this derivatization, a trifluoromethyl group was found to behave as a much larger substituent than a decyl group.
TL;DR: In this paper, the preparation of 1,3-dienes with organocuprates has been studied in a stochastic double-bond system with a stepwise approach, where only one reactive acetate leaving group is available for the cuprate reagent at any given time.
Abstract: Sterically Hindered Double Bond Systems, 2 — On the Preparation of Highly Substituted 1,3-Dienes
Highly alkylated 1,3-dienes may be prepared by treatment of 2-butyne-1,4-diol derivatives with organocuprates in good yield Thus, the 2,3-dialkylated butadienes 6a—d are obtained by treating the diacetate 4 with two equivalents of the cuprates prepared from the Grignard reagents 5a—d with CuBr/LiBr Analogously, meso-14 is converted into a mixture of the di-tert-butyl-2,4-hexadienes (Z,E)- and (Z,Z)-15 The procedure may be extended to the synthesis of unsymmetrically substituted 1,3-dienes by either treating the appropriate diacetates with two equivalents of the same cuprate as examplified by the conversion of 18 into 19a and 19b or by employing a stepwise approach in which only one reactive acetate leaving group is available for the cuprate reagent at any given time, thus allowing the change of the organometallic reagent in the course of the synthesis (preparation of the dienes 26 from the monoacetates 22) The mechanisms of these reactions as well as those of several reactions leading to sideproducts are discussed
TL;DR: N-Boryl imines obtained from partial reduction of nitriles with borane–tetrahydrofuran have been alkylated with organolithium or Grignard reagents to afford secondary carbinamines in moderate to excellent yields.
Abstract: N-Boryl imines obtained from partial reduction of nitriles with borane–tetrahydrofuran have been alkylated with organolithium or Grignard reagents to afford secondary carbinamines in moderate to excellent yields.
TL;DR: In this article, the α-monoalkylated camphors 2-7 and 2-alkylisoborneols 9a-13a remained more or less within the camphor-eucalyptus odour profile and the disubstituted (iso)borneols 22-25 possess a strong patchouli scent.
Abstract: From camphor (1) the ketones 2–7 were prepared by α-alkylation, and the tertiary alcohols 9–17 by Grignard reaction. The disubstituted (iso)borneols 21–26 could be obtained by Grignard reaction of 2–4 with MtMgI or allyl magnesium halide. Reaction of 2–4 with EtMgl afforded the secondary alcohols 18–20 by reduction. Olfactive evaluation showed that the α-monoalkylated camphors 2–7 as well as the 2-alkylisoborneols 9a–13a remained more or less within the camphor-eucalyptus odour profile. However, 14a–16a and the disubstituted (iso)borneols 22–25 possess a strong patchouli scent. The structure of a sterically hindered, rigid tertiary alcohol with 13 to 15 C-atoms should be responsible for this phenomenon.
TL;DR: In this article, the corresponding diastereomeric pairs of 7,8-dideoxyoct-7-eno-1,4-furanoses were determined after oxidative cleavage of the terminal double bond and reduction of the aldehyde by conversion of the resulting heptoses into the known corresponding corresponding per-O-acetylated heptitols.
TL;DR: In this article, 6-phenyl-4-oxa-7, 7a-diazaperhydroindans (5 and 6) were synthesized by condensation of chiral 2-hydroxyethylhydrazines prepared from (R)-phenylglycinol with γ-chlorobutyraldehyde.
Abstract: New heterocyclic compounds, 6-phenyl-4-oxa-7, 7a-diazaperhydroindans (5 and 6), were synthesized by condensation of chiral 2-hydroxyethylhydrazines prepared from (R)-phenylglycinol with γ-chlorobutyraldehyde. The stereoselective Grignard reaction of 5 and 6 proceeded to give chiral 2-substituted 1-[N-(2-hydroxy-1-phenylethyl)amino] pyrrolidines(7a-d and 8a-d). The structures of these products were determined by comparison with authentic samples, and the reaction mechanism is proposed to involve an intermediate iminium salt.
TL;DR: In this paper, a regioselective synthesis of 8,9-dichloro-2,3,4,5-tetrahydro-1H-2-benzazepine (LY134046, 10) and its 3-methyl analogue 26 from 6,7-dimethylo-3-hydroxyphthalide (6,7)-phthalide was described, where the key step involved 1,4-hydride addition to the α,β-unsaturated nitrile 17 to give the saturated nitri
TL;DR: In this article, the relative ratio of carbon (normal)-and oxygen (abnormal)-attacked products are usually afforded in the Grignard reaction of α-diketones.
Journal Article•
TL;DR: Several reactions of 6,6a,7,8,9,10,10a,11-octahydro-11-oxodibenzo[b,e]thiepins and -oxepins were studied, which included reduction, oxidation, Grignard reaction, thiation, and the Wittig reaction.
Patent•
07 May 1991
TL;DR: In this article, a compound expressed by formula I (R is H or methoxy; pyridyl group is bonded to 4position of phthalazine at 2, 3 and 4 position thereof).
Abstract: NEW MATERIAL:A compound expressed by formula I (R is H or methoxy; pyridyl group is bonded to 4-position of phthalazine at 2, 3 and 4 position thereof). EXAMPLE:4-(3-Pyridyl)-1(2H)phthalazinone. USE:A synthetic intermediate for platelet agglutination suppressing agent. PREPARATION:According to the reaction formula, 2-(2-bromophenyl)-4,4- dimethyl-2-oxazoline expressed by formula II is subjected to Grignard reaction with 2-, 3- or 4-pyridine aldehyde to give a compound expressed by formula IV. Hydroxyl group of the compound expressed by formula IV is oxidized to afford a ketone body expressed by formula V, which is further treated with an acid to cleave an oxazoline ring and then reacted with hydrazine to provide the compound expressed by formula I.
TL;DR: Poly(N-ethyl 3.7-phenothiazinediyl) and poly(n-ethyl co-acetylene) as discussed by the authors were synthesized by homo-and copolycondensation of N-ethyl and 1.2Dibromoethene using a Grignard reaction and NiCl 2 or NiCl2.2PPh3 as catalyst.
Abstract: Poly(N-ethyl 3.7-phenothiazinediyl) (1) and poly (N-ethyl 3.7-phenothiazinediyl-co-acetylene) (2) were synthesized by homo- and copolycondensation of 3.7-dibromo N-ethylphenothiazine and 1.2-dibromoethene using a Grignard reaction and NiCl2 or NiCl2.2PPh3 as catalyst. Polymers are soluble in common organic solvents and after doping with iodine have an electrical conductivity of 10−7 −10−6
$$\Omega ^{ - 1} $$
cm−1.
Patent•
01 Jun 1991
TL;DR: In this article, a compound of formula I (R is 6-10C alkyl 1,5-disubstituted with lower alkyls), eg 7-(1,5dimethylhexyl)-3-phenyl-4H-1-benzopyranone, can be produced by using a compound (R 1 ) of formula II as a starting raw material, protecting the hydroxyl group with a protection group R 2, introducing 4-substitized 5-9C side chain by Grignard reaction, eliminating the protection group
Abstract: PURPOSE: To provide the subject new compound useful as a therapeutic agent for osteoporosis CONSTITUTION: The compound of formula I (R is 6-10C alkyl 1,5-disubstituted with lower alkyl), eg 7-(1,5-dimethylhexyl)-3-phenyl-4H-1-benzopyranone The compound of formula I can be produced by using a compound of formula II (R 1 is lower alkyl) as a starting raw material, protecting the hydroxyl group with a protection group R 2 , introducing 4-substituted 5-9C alkyl side chain by Grignard reaction to obtain a compound of formula III, eliminating the protection group and removing the hydroxyl group by dehydration, reducing the double bond of the formed compound by hydrogenation reaction, bonding the obtained phenol derivative to a phenyl acetyl halide by Friedel-Crafts reaction and subjecting the obtained deoxybenzoin compound of formula IV to cyclization reaction COPYRIGHT: (C)1992,JPO&Japio
Patent•
19 Dec 1991
TL;DR: In this paper, the preparation of N-substituted vicinal amino alcohol derivatives from hydroxyl-protected cyanohydrin derivatives by successive Grignard reaction, transimination using a primary amine, reduction of the resulting imine and removal of the hydroxy-protecting group is described.
Abstract: The present invention is concerned with the preparation of erythro N-substituted vicinal aminoalcohol derivatives from hydroxyl-protected cyanohydrin derivatives by successive Grignard reaction, transimination using a primary amine, reduction of the resulting imine and removal of the hydroxyl-protecting group. The products are obtained either as a racemate or in an optically pure form, depending upon the stereochemical composition of the cyanohydrin derivatives.
Journal Article•
TL;DR: In this article, a stereocontrolled synthesis of ()-isocomene via selective monoketalization of tricyclo[6.3.0]undeca-4,7-dione(13) was reported.
Abstract: A stereocontrolled synthesis of ()-isocomene (1) via selective monoketalization of tricyclo[6.3.0.]undeca-4,7-dione(13) was reported. Grignard reaction of bicyclic enone 10, which was prepared from 2-methyl-1,3-cyclopentadione, gave the 1,4-addition product 11. The subsequent aldol condensation product 12 was converted to mesyl derivative 13. Transformation from 13 to the desired product 19 was achieved by a series of reactions, i.e., the selective monoketalization at C-4 carbonyl group, the elimination of a mesyl group, Birch alkylation, methylation at C-6, the reduction of carbonyl group, the dehydration of alcohol 18, and hydrolysis of the ketal group.
TL;DR: In this article, the synthesis of [20,21-13C2]-progesterone from androst-4-ene-3,17-dione is described and labels are introduced by two procedures, namely, condensation of 1 with K13CN and Grignard reaction of nitrile derivative 7 with [13C]-methylmagnesium iodide.
Abstract: The synthesis of, [20,21-13C2]-progesterone (9) from androst-4-ene-3,17-dione (1) is described. Labels were introduced by two procedures, namely, condensation of 1 with K13CN and Grignard reaction of nitrile derivative 7 with [13C]-methylmagnesium iodide. Location of labels was confirmed by 13C-NMR spectroscopy.
TL;DR: In this article, the assymetric cross-coupling reactions resulted in low enatiomeric excess up to 11% in the case of acetophenone and showed that the Ni and Pd complexes of these ligands were tested in the Grignard cross coupling reaction.