Showing papers on "Grignard reaction published in 1975"
TL;DR: In this article, the relative configurations of natural type of racemic blastmycinone and its all diastereomers were completely established by the synthesis of natural (+)blast mycinone from methyl 4,6-O-benzylidene with butylmagnesium chloride.
Abstract: Natural (+)blastmycinone [(+)1a] and its three (2R)-diastereomers [(+)1b, (−)1c, and (−)1d] were synthesized through stereospecific routes via the corresponding (−)blastmycinolactol [(−)2a] and its diastereomeric hydroxylactones [(+)2b, (−)2c, and (−)2d] from methyl 4,6-O-benzylidene-3-C-butyl-3-deoxy-α-D-altropyranoside (4) prepared by the Grignard reaction of methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside (3) with butylmagnesium chloride. By the synthesis the relative configurations of natural type of racemic blastmycinone and its all diastereomers were completely established.
34 citations
TL;DR: In the reaction of benzophenone with phenylmagnesium bromide, the concentration and life-time of the ketyl radical were influenced greatly by the substitution of ortho-hydrogen atoms of both the two reactants by methyl group as discussed by the authors.
Abstract: In the reaction of benzophenone with phenylmagnesium bromide, the concentration and life-time of the ketyl radical were influenced greatly by the substitution of ortho-hydrogen atoms of both the two reactants by methyl group. From the results of visible absorption and ESR measurements and also of product-analysis, the ketyl radical was considered to be a common intermediate towards normal and abnormal reaction products. The existence of an equilibrium between monomeric and dimeric states of the ketyl radical was also proposed.
21 citations
TL;DR: In this article, the reaction of 2,4,6-trimethylbenzophenone with phenyl-MgBr in tetrahydrofuran was examined by ESR technique.
Abstract: The reaction of 2,4,6-trimethylbenzophenone with phenyl-MgBr in tetrahydrofuran was examined by ESR technique. A high amount of the ketyl radical was detected. An electron-transfer mechanism was proposed to explain the formation of o-biphenylyl mesityl ketone.
17 citations
TL;DR: The radical in the title reaction gave an ESR spectrum different from that of potassium-ketyl as discussed by the authors, and the reason for this difference was ascribed to the suppression of the twisting vibration caused by aggregate-formation.
Abstract: The radical in the title reaction gave an ESR spectrum different from that of potassium-ketyl. From studies using the deuterium label technique, the reason for this difference was ascribed to the suppression of the twisting vibration caused by aggregate-formation.
13 citations
TL;DR: The sidechain of 25-hydroxycholesterol was constructed stereospecifically on the androstane skeleton via addition of an ethyl acetate unit to C-17 and subsequent alkylation of the resulting ester C-20 with a C5 unit; the remaining carbon atom (C-27) was added by a Grignard reaction.
Abstract: The side-chain of 25-hydroxycholesterol was constructed stereospecifically on the androstane skeleton via addition of an ethyl acetate unit to C-17 and sub-sequent alkylation of the resulting ester C-20 with a C5 unit; the remaining carbon atom (C-27) was added by a Grignard reaction.
8 citations
TL;DR: The carcinogen, benzo[a]pyrene, was tritiated by two methods: exchange reaction with T 2 SO 4 at the 1, 3 and 6 positions and quenching of a Grignard reagent prepared from 6-iodo-benzo-pyrene with T2 O which gave almost exclusively 6-tritiated material.
7 citations
TL;DR: Pentazocine was synthesized from L-tyrosine using n-Benzylation of methyl ester followed by Schotten-Baumann reaction of the amine to afford the amide in good yield.
Abstract: Pentazocine (1) was synthesized from L-tyrosine (2). N-Benzylation of methyl ester (3), obtained from L-tyrosine, followed by Schotten-Baumann reaction of the amine (4), gave the amide (5). Dieckmann reaction of 5 gave the racemic β-ketoester (6), whose methylation followed by decarboxylation afforded the ketoamide (8). Grignard reaction gave the carbinol (9), which was cyclized with hydrobromic acid to afford the amide (10) in good yield. Reduction of 10 with sodium bis-(2-methoxyethoxy) aluminum hydride or lithium aluminum hydride gave the amine (11), which had already been converted into pentazocine.
6 citations
TL;DR: MeMgI reacts with O-alkyl S-methyl phenylphosphonothiolates to displace either the methylthio group with retention of configuration at phosphorus or the alkoxy group with inversion.
Abstract: MeMgI reacts with O-alkyl S-methyl phenylphosphonothiolates to displace either the methylthio group with retention of configuration at phosphorus or the alkoxy group with inversion, the competition depending on the nature of the alkoxy group.
6 citations
TL;DR: The stereoselectivity of three kinds of electrophilic reactions, vis osmium tetroxide oxidation, bromohydrination and peracid epoxidation of 24-nor-5α-chol-22-en-3β-ol 4 was investigated by the analysis of the products as discussed by the authors.
Abstract: The stereoselectivity of three kinds of electrophilic reactions, vis. osmium tetroxide oxidation, bromohydrination and peracid epoxidation of 24-nor-5α-chol-22-en-3β-ol 4 was investigated by the analysis of the products. The conformations II and III are proposed as participating in the transition states in the course of these reactions. The stereochemistry of the Grignard reaction on the 22-aldehyde is also discussed.
6 citations
TL;DR: Lavandulyl methyl ether was prepared by the following reactions as discussed by the authors : the addition of chloromethyl methyl ether to prenyl chloride in the presence of stannic chloride afforded 1, 3-dichloro-2-methoxymethyl-3-methylbutane, which was then treated in DMF to give the dehydrochlorination product, 2-methyl-3methoxidemethyl-4-chlorobutene-1.
Abstract: Lavandulyl methyl ether was prepared by the following reactions : The addition of chloromethyl methyl ether to prenyl chloride in the presence of stannic chloride afforded 1, 3-dichloro-2-methoxymethyl-3-methylbutane, which was then treated in DMF to give the dehydrochlorination product, 2-methyl-3-methoxymethyl-4-chlorobutene-1. The Grignard reaction of the butene derivative with methallyl chloride gave lavandulyl methyl ether. The total yield of lavandulyl methyl ether was 3540% based on isoprene.
1 citations
TL;DR: In this article, the reaction of cyclooctatetraene oxide with several organometallic reagents and metal salts was investigated with reference to skeletal change of the ring and showed that the addition of HMPA in the Grignard reaction results in reduction of the reactivity and formation of the isomerized cyclic trienone.
Abstract: The reaction of cyclooctatetraene oxide ( 1 ) with several organometallic reagents and metal salts were investigated with reference to skeletal change of the ring. LAH causes ring cleavage to yield octa-2,4,6-trienal along with the formation of cycloocta-3,5-dienol. Ethylmagnesium bromide and triethylaluminum afford ethyl(cyclohepta-2,4,6-trienyl)methanol in good yields, but the addition of HMPA in the Grignard reaction results in reduction of the reactivity and formation of the isomerized cyclic trienone. A similar medium effect by HMPA or solvent is found in the reaction of 1 with ethyllithium which affords 5-ethylcycloocta-2,6-dienone (70·2%) in ether, and also in the metal salts (MgBr 2 , LiBr, and LiClO 4 ) induced isomerization giving cycloheptatrienylcarboxyaldehydes and phenylacetaldehyde. The diverse nature of the products in the reactions is accounted for by the formation of homotropylium cation intermediates.
TL;DR: In this paper, the preparation of the C-17a epimeric D-homo-5α, 14β-pregnan-20-ones (VIII, IX) has been undertaken.
Abstract: In order to obtain the key intermediates leading to the D-homo cardenolide analogs, the preparation of the C-17a epimeric D-homo-5α, 14β-pregnan-20-ones (VIII, IX) has been undertaken. Upon catalytic hydrogenation the Δ14, 16-dien-17a-one (IV), derivable from D-homo-5α-androstan-17a-one (I) by repeated unsaturation, provided the desired 14β-steroid (V) as a main product. Introduction of a C2 unit into C-17a was attained by the Grignard reaction with ethynylmagnesium bromide, followed by hydration with mercury resin to yield D-homo-5α, 14β, 17a-pregn-17-en-20-one (VII). Subsequent hydrogenation over palladium-on-charcoal afforded IX and VIII in a ratio of ca. 5 to 1. Configurational assignment of the side chain in IX was accomplished by transforming the 20-oxime (XIV) into the 17aα-acetamido derivative (XV) by the Beckmann rearrangement.
TL;DR: In this article, Δ1-trans-octenoic-3-14C acid was prepared by a Grignard reaction with BaCO3- 14C and 1-bromo-pentane.
Abstract: In a first step, Δ1-trans-octenoic-3-14C acid was prepared by a Grignard reaction with BaCO3-14C and 1-bromo-pentane, followed by reduction of the obtained hexanoic-1-14C acid to hexanal-1-14C via the n-hexanol-1-14C. The produced hexanal-1-14C, by condensing with malonic acid gives the request Δ1-trans-octenoic-3-14C acid. In a second step, olivetolic-6-14C acid, ethyl ester was prepared by condensing the Δ1-trans-octenoic-3-14C acid, methyl ester with ethyl acetoacetate followed by bromination and catalytic hydrogenation.
TL;DR: In this article, the relative configurations of natural type of racemic blastmycinone and its all diastereomers were completely established by the synthesis of natural (+)blast mycinone from methyl 4,6-O-benzylidene with butylmagnesium chloride.
Abstract: Natural (+)blastmycinone [(+)1a] and its three (2R)-diastereomers [(+)1b, (−)1c, and (−)1d] were synthesized through stereospecific routes via the corresponding (−)blastmycinolactol [(−)2a] and its diastereomeric hydroxylactones [(+)2b, (−)2c, and (−)2d] from methyl 4,6-O-benzylidene-3-C-butyl-3-deoxy-α-D-altropyranoside (4) prepared by the Grignard reaction of methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside (3) with butylmagnesium chloride. By the synthesis the relative configurations of natural type of racemic blastmycinone and its all diastereomers were completely established.
TL;DR: In this article, the reaction of 2,4,6-trimethylbenzophenone with phenyl-MgBr in tetrahydrofuran was examined by ESR technique.
Abstract: The reaction of 2,4,6-trimethylbenzophenone with phenyl-MgBr in tetrahydrofuran was examined by ESR technique. A high amount of the ketyl radical was detected. An electron-transfer mechanism was proposed to explain the formation of o-biphenylyl mesityl ketone.