Showing papers on "Alkylation published in 1974"

Phytosterol side chain biosynthesis.

Abstract: The typical plant sterols contain a substituent at C-24 of the side chain. This can be a methylene, ethylidene, methyl, or ethyl group; with the last three groups, all possible isomers have been reported in nature. The C-24 alkyl groups are derived by a transmethylation reaction from methionine. The details of several distinct alkylation mechanisms, which are now recognized in a range of lower and higher plants, have been reviewed. The operation of these different routes may have some phylogenetic significance.

Synthesis of prostaglandins by conjugate addition and alkylation of a directed enolate ion. 4,5-allenyl prostaglandins

Abstract: Over the previous two decades many elegant syntheses of prostaglandins, which in more sophisticated forms, allow the stereospecific introduction of the various asymmetric carbons have been accomplished. However, among these approaches the cuprate addition/enolate alkylation of suitable cyclopentenone {sup 2} stands out because of brevity and convergence. The recent reports by Noyori{sup 3} and Corey{sup 4} and their colleagues have reduced to practice the conversion of 4-alkoxycyclopentenones to prostaglandin E{sub 2} (PGE{sub 2}) by conjugate addition of an organocopper derivative of the lower side chain followed by alkylation of the resulting carbanion with methyl 7-halohept-2-enoate. The subject of this paper is application of the Tardella tin enolate alkylation developed by Noyori to the synthesis of 4, 5-allenic prostaglandins, a pharmacologically important class of compounds. The authors results demonstrate that the tandem alkylation of an enone precursor with a cuprate reagent followed by alkylation of the corresponding tin enolate with bromide reagent is a viable synthetic method for 4,5-didehydro-PGE{sub 2}. Because the optically active forms of 1 and the vinyl iodide precursor of the PGE{sub 2} lower side chain have been employed to produce a single enantiomer of PGE{sub 2}, the extension of the methodology described here to the synthesis ofmore » single enantiomers of 4a awaits only the preparation of the separate enantiomers of allene 14.« less

New Approach to Derivatization and Gas-Chromatographic Analysis of Barbiturates

Abstract: A recently developed procedure for alkylation of organic acids has proven extremely successful for preparation of volatile alkyl derivatives of the barbiturates for gas-chromatographic analysis. Soluble salts are formed in a mixture of N,N-dimethylacetamide and methanol. These in turn react rapidly with alkyl iodides to form the corresponding alkyl derivatives. The butyl derivatives of barbiturates, prepared in this manner, are separable by high-resolution gas-chromatography. Any of 14 barbiturates can be determined simultaneously or separately (although there is some overlap with certain uncommon barbiturates). The butyl derivatives of several barbiturates that are unresolved in the form of underived compounds or methyl esters can be resolved, thus overcoming many previous analytical limitations.

Regiospecific Acylation, Alkylation, and Aldol Condensation using magnesium enolates resulting from the conjugate addition of grignard reagents to α, β-unsaturated ketones

Abstract: The magnesium 3,3-dimethylcyclohex-1-enolate 1i, formed in the copper catalyzed addition of methylmagnesium iodide to 3-methylcyclohex-2-enone, has been subjected to regiospecific electrophilic reactions such as acylation, alkylation, and aldol condensation in order to find a new access to the damascones, ionones and carotenoids. By way of illustration a new synthesis of γ-damascone is described.

Alkylation of phenols

Abstract: Improvement in a method for producing para-alkylated phenols comprising reacting (A) a phenol and (B) an alkylating agent in the presence of (C) an alkylation catalyst and resulting product. This improvement comprises using as (C) an aryl sulfonic acid selected from the class of highly acidic aryl sulfonic acids having a K value of at least 3.8 × 10- 3 including para-chlorobenzene sulfonic acid, 4,4'-diphenyldisulfonic acid, nitrobenzenesulfonic acids, 2,4,6-trinitrobenzenesulfonic acid and meta-benzenedisulfonic acid and also trifluoromethanesulfonic acid. These acid catalysts are also very effective in rearranging ortho and meta substituted phenols to parasubstituted phenols allowing use of normally discarded by-products as starting materials.

Studies on intramolecular alkylation. V. Intramolecular alkylation of the aromatic ring in tetrahydronaphthyl diazomethyl ketones

Abstract: The acid-catalysed reactions in weakly nucleophilic environments of 2-diazoacetyl-l,2,3,4-tetrahydronaphthalene (ll), of 6-diazoacetyl-5,6,7,8-tetrahydro-2-naphthol (2), of 6-diazoacetyl-5,6,7,8- tetrahydro-2-naphthyl methyl ether (3) and its 2,8 and 2,5 isomers (14) and (17), and of 6-diazo- acetyl-5,6,7,8-tetrahydro-6-trifluoroacetoxy-2-naphthyl methyl ether (9) have been studied. Several of the spirocyclohexa-2,5-dienone derivatives prepared thus, (4), (8) and (16), provide potential intermediates or models for the synthesis of tetracyclic diterpenoids.

Studies on intramolecular alkylation. VI. ortho-Alkylation in phenolic diazoketones: the preparation of intermediates containing the Cyclohexa-2,4-dienonemoiety suitable for gibberellin synthesis

Abstract: Simple efficient syntheses of 8-hydroxy- and 8-methoxy-2-tetralones (9) and (10), 1,2,3,4-tetrahydro-8- hydroxy-2-naphthoic acid (5), 1,2,3,4-tetrahydro-2-hydroxy-8-methoxy-2-naphthoic acid (8), 1,2,3,4-tetrahydro-2,s-dihydroxy-2-naphthoic acid (7) and 1,2,3,4-tetrahydro-5-hydroxy-2-naphthoic acid (20) are described. The acid-catalysed reactions of the diazoketones derived from (5) and (20) gave good yields of tricyclic ketones (3) and (4) incorporating a cyclohexa-2,4-dienone moiety. The potential of (3) for gibberellin synthesis is examined.

Aromatic amine alkylation

Abstract: Aromatic amines having a hydrogen atom on at least one nuclear carbon atom ortho to an amine group (e.g., aniline) are selectively orthoalkylated by adding a catalytic amount of an alkyl aluminum halide such as diethyl aluminum chloride to the aromatic amine and then heating the resultant mixture to about 100*-500*C in the presence of an olefin. The process may also be carried out in the added presence of an aluminum anilide.