Showing papers on "Grignard reaction published in 1982"

Synthetic studies of rifamycins. V. A chiral synthesis of an ansa-chain compound for the C-17 - C-29 portion of rifamycin W.

Abstract: The chiral synthesis of methyl 5,7,9-tri-O-acetyl-2-C-(acetoxymethyl)-2,4,6,8,10,11,12-heptadeoxy-4,6,8,10-tetra-C-methyl-aldehydo-L-glycero-L-talo-L-manno-(E)-11-tridecenuronate 1-(dimethyl acetal) (III), a useful synthetic segment for the C-17-C-29 portion of rifamycin W, is described. The key intermediate, 3-O-(t-butyldimethylsilyl)-2,4,7-trideoxy-5,6-O-isopropylidene-2,4-di-C-methyl-aldehydo-D-glycero-D-talo-heptose (28) was synthesized in 30% yield from methyl 4,6-O-benzylidene-3-deoxy-3-C-methyl-α-D-glucopyranoside in 15 steps. The synthesis involves key steps of highly stereoselective Grignard reaction and regiospecific cis-epoxide ring-opening reaction. The condensation of 28 with 3,3-diethoxy-2-lithio-1-propene afforded about 1.6:1 excess of the “Cram” product (30, 56% yield). The desilylation of 30 followed by homogeneous hydrogenation with (Ph3P)3RhCl gave only the erythro product 34. 3,5-Di-O-benzyl-2,4,6-trideoxy-2,4,6-tri-C-methyl-L-glycero-L-manmo-heptodialdose 1-(diethyl acetal) derived fr...

REACTIONS OF PHENYLYTTERBIUM σ COMPLEX WITH BENZOYL CHLORIDE AND METHYL BENZOATE: A SELECTIVE KETONE SYNTHESIS

Abstract: Phenylytterbium iodide (Ph–Yb–I) has been found to react with benzoyl chloride to give both triphenylcarbinol and benzophenone. When Ph–Yb–I is added inversely to benzoyl chloride, especially in the presence of FeCl3, the ketone is obtained selectively in modest yields in contrast to the Grignard reaction.

Purines. V. Reaction of 9-Phenyl-9H-purine-6-carbonitrile with Nucleophilic Reagents

Abstract: The reaction of 9-phenyl-9H-purine-6-carbonitrile (1) with nucleophilic reagents occurred by addition of the reagent across the C-N triple bond of the cyano group, and substitution of the cyano group was not observed. Thus, the reactions with hydroxylamine, hydrazine, amines, Grignard reagents, and 98% sulfuric acid gave the corresponding amidoxime (2), amidorazone (3), amidines (4), ketones (5), and amide (7), respectively. Alcoholysis of 1 gave the ester (6) and 7 together with the ring fission product of the imidazole portion, alkyl 5-amino-6-anilino-4-pyrimidine-carboxylate (8). Amides (10), the hydroxamic acid (11), and the hydrazide (12) were prepared from the methyl ester (6a).

Cross-coupling reaction of aryl grignard reagents with aromatic halides catalyzed by bis(acetylacetonato)nickel(II).

Abstract: A series of cross-coupling reactions of aryl Grignard reagents with aromatic iodides catalyzed by bis (acetylacetonato) nickel (II) was studied to establish reaction conditions under which the cross-coupling proceeded selectively and quantitatively. Under the standard conditions thus selected, the coupling reactions proceeded within a few hours by a simple procedure and gave very pure product in high yield. Thus, the Kharash-type cross-coupling reaction was found to be very useful for the synthesis of a variety of polyphenyls. With some reactants of more or less orowded geometry, the reaction resulted in rather low yields of polyphenyls. This cross-coupling was successfully applied to the synthesis of a new compound, 2, 6, 2', 6'-tetraphenylbiphenyl, having a highly non-planar arrangement of π-systems.

Process for the continuous production of alcohols

Abstract: A process for the continuous production of an alcohol from an organic halide, metallic magnesium and an organic carbonyl compound according to the Grignard reaction, which process comprises continuously supplying a portion of an intended amount of the organic halide and an intended amount of the metallic magnesium with an inert solvent to a first reaction zone whereby the reaction between the organic halide and the metallic magnesium proceeds to give the Grignard reagent, and continuously passing the reaction mixture comprising the Grignard reagent and the unreacted metallic magnesium from the first reaction zone to a second reaction zone to which the remaining portion of the organic halide and an intended amount of the organic carbonyl compound, optionally with an inert solvent, are continuously supplied whereby the Grignard reaction proceeds to give the Grignard reaction product, followed by subjecting the reaction mixture comprising the Grignard reaction product from the second reaction zone to hydrolysis to give the alcohol.

Synthesis, conformation, and chirality of di-O-methylsequirin D, a biogenetically novel metabolite of Sequoia sempervirens

Abstract: The synthesis of (±)-di-O-methylsequirin D (14; R = H) is reported. A Grignard reaction between 3,3-ethylenedioxypropylmagnesium bromide and deoxyanisoin gave the key alcohol (5), which was transformed into (14) by way of the acid (11) and the tetralone (12). Measurement of the 3-H2,4-H coupling constants in (14; R = D) show the compound to have a 4-axial anisyl substituent, while c.d. data indicate a left-hand skewed styrene geometry in the dimethyl ether of the natural norlignan (2). The absolute configuration of (2) is hence deduced as 1R. The biosynthesis of sequirin-D and the origin of the m-hydroxycinnamate unit are discussed.

Preparation of furfuryl alcohols

Abstract: PURPOSE:To obtain the titled substance in high yield using a small amount of THF without fear of precipitated crystal, by adding Mg to a mixed solvent of THF and an aromatic hydrocarbon, so that a furfural is simultaneously reacted with (alpha-methyl)allyl chloride. CONSTITUTION:A furfural shown by the formulaI(R1 is H or CH3) is reacted with Mg and (alpha-methyl)allyl chloride, and hydrolyzed to give a compound shown by the formula II (R2 is allyl, or alpha-methylallyl). In the reaction, a mixed solvent of THF and an aromatic hydrocarbon (e.g., benzene) is used a reaction solvent, Mg is added to the mixture, in which the furfural is simultaneously reacted with allyl chloride, etc. The amount of THF used is >=0.5 that of the furfural, and the amount of the aromatic hydrocarbon is >=1 that of the furfural. The reaction temperature is -20-60 deg.C. EFFECT:Since the Grignard reaction product is not precipitated and crystallized, the removal of the reaction heat and stirring are unnecessary. The solvent is recovered easily. USE:An intermediate for an agricultural chemical, drug, and perfume.

Preparation of e-alkenyl grignard reagent

Abstract: PURPOSE:To obtain the titled compound useful as an organic synthetic raw material, particularly a tri-substitute olefin, by reacting a di-substituted acetylene with an alkylmagnesium halide in the presence of a catalyst. CONSTITUTION:A di-substituted acetylene of the formula R -C C-R (R is alkyl, aryl or silyl which may have a substituent group as far as it is inert to the Grignard reaction) is reacted with an alkylmagnesium halide of the formula RMgX (R is propyl, isopropyl, isobutyl, etc.; X is Cl, Br or I) in the presence of a catalyst of the formula Cp2TiCl2 (Cp is cyclopentadienyl or a derivtive thereof) in a solvent, e.g. diethyl ether, at room temperature to give the aimed substance. The high stereoselectivity is obtained according to the kind of the acetylene.

Synthesis of triamcinolone acetonide-4-14C

Abstract: The free hydroxyl groups in triamcinolone acetonide (1) were protected as silyl ethers to give the bis-silyloxy derivative 4. Compound 4 was then hydrogenated over 5% palladium on carbon to give the Δ4-3-oxo steroid 5 which was then converted to the enol-lactone 7 under selective reaction conditions. The enol-lactone 7 was subjected to Grignard reaction with 14C-methylmagnesium iodide to give an adduct 8a which on subsequent treatment with lithium 2,6-di-t-butylphenoxide gave 4-14C-Δ4-3-oxo derivative 9. Compound 9. was heated with selenium dioxide in t-butanol containing pyridine to give the Δ1,4-3-oxo derivative 10. Removal of the silyl protecting groups was readily accomplished by heating 10 with hydrochloric acid in methanol-tetrahydrofuran solution to give the title compound 11.

Reactions of phenylytterbium σ complex with carbonyl compounds. a new grignard-type reagent having unusual reactivity toward esters and ketones

Abstract: Phenylytterbium iodide has been found to react with ketones, aldehydes, esters, and nitriles to give alcohols and/or ketones. The reactions with esters at low temperature give ketones as main products, and the reactivity of esters to Ph–Yb–I is higher than that of ketones in contrast to the Grignard reaction.

Reactions of phenylytterbium σ complex with benzoyl chloride and methyl benzoate: a selective ketone synthesis

Abstract: Phenylytterbium iodide (Ph–Yb–I) has been found to react with benzoyl chloride to give both triphenylcarbinol and benzophenone. When Ph–Yb–I is added inversely to benzoyl chloride, especially in the presence of FeCl3, the ketone is obtained selectively in modest yields in contrast to the Grignard reaction.