Electrophilic Double Bond Research Articles

Synthesis of cyclopentenones and butenolides by reaction of the lithium salt of P,P-diphenyl-P-(alkyl)(N-phenyl)phosphazenes with electrophilic double and triple bonds

Lithium P,P-diphenyl-P-(alkyl)(N-phenyl)phosphazenes act as bidentate reagents towards electrophilic olefins and acetylenes. The reactions with dimethyl acetylenedicarboxylate (DMAD) and dimethyl maleate afford cyclopentenones, while with methyl benzoylpropiolate the products obtained are butenolides with a quaternary carbon atom in position 5 of the heterocycle. The use of less activated substrates (methyl phenylpropiolate, methyl cinnamate, and dimethyl oxalate) allowed the isolation of C-acylated aminoylide or phosphazene derivatives. A reaction mechanism is proposed based on a tandem process involving the regioselective C-acylation of the carbon α to the phosphorus, followed by a cyclisation process promoted by the intramolecular Michael addition of the nitrogen of the PN linkage to an electrophilic double or triple carbon–carbon bond.

ChemInform Abstract: Catalytic Oxidative Cleavage of Electrophilic Double Bonds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic Oxidative Cleavage of Electrophilic Double Bonds

Abstract Oxidative cleavage of a variety of electrophilic double bond substrates has been effected under mild reaction conditions by sodium metaperiodate or sodium hypochlorite catalyzed by ruthenium oxide.

Chemoselective ring construction from unsymmetrical 1,6-dienes via radical addition of sulfonyl halides

The sulfonyl radical-promoted cyclizations of 1,6-unsymmetrical dienes can be totally chemoselective. The addition of tosyl halides to various 1,6-dienes bearing both a nucleophilic and an electrophilic double bond clearly indicates that the attractive property is not related to the generally accepted electrophilic nature of tosyl radical. The chemoselectivity is likely to originate from the reversibility of the first step, i.e. tosyl radical addition to the double bond, which favors the formation of the adducts resulting from the one intermediate radical that cyclizes faster

ChemInform Abstract: The Action of Sodium Hydrogen Telluride on Olefins.

AbstractThe action of NaTeH on non‐electrophilic C=C bonds is investigated.

ChemInform Abstract: Intramolecular Cyclization of ω‐Primary Amino Electrophilic Olefins to Functionalized Pyrrolidines and Piperidines.

Abstract The intramolecular 1,4-Michael type addition of in situ chemoselectively generated primary amines bearing an electrophilic double bond in the ω position leads to functionalized pyrrolidines and piperidines under very mild conditions.

Stereochemical and Mechanistic Aspects of the Aprotic Conjugate Addition Reactions of the Carbanions of Octenyl Sulfides and Octenyl Thiocarbamates With 4-Tert-Butoxycyclopent-2-Enone in the Presence of Hexamethylphosphoric Triamide

The carbanions of (E)- and (Z)-1-(pheny1thio)oct-2-ene, (E)-1-(methy1thio)- and 1-(t-butyl- thio )oct-2-ene, N,N-dimethyl S-[(E)-oct-2-enyllthiocarbamate and (E)-oct-2-enyl benzothiazole undergo conjugate addition to 4-t-butoxycyclopent-2-enone in the presence of hexamethyl - phosphoric triamide ( hmpa ) in tetrahydrofuran at -70� to give as predominant products diastereomeric mixtures of syn and anti allylic sulfides arising from reaction through C1 of the octenyl carbanions. Also formed in some cases are small amounts of diastereomeric mixtures of syn and anti vinylic sulfides arising from reaction through C3 of the octenyl carbanions. In the absence of the hmpa, carbonyl addition is the major reaction pathway of the carbanions of each of the (E)- and (Z)- octenyl thiocarbamates. The constitutions and stereostructures of all the products have been established through chemical shift and coupling constant correlations of their IH n.m.r. data obtained at 400 MHz. The relative proportions of the regioisomeric allylic and vinylic sulfides are dependent both upon the nature of the non-allylic substituent attached to the sulfur atom, and the geometry of the double bond in the starting octenyl sulfide. While there is no apparent connection between the electronic properties or sizes of the non-allylic substituent and the diastereomer ratios of the allylic and vinylic sulfides, it is noted that the (2)-(phenylthio) octene delivers an allylic sulfide mixture enriched in the syn isomer. It is concluded that the carbanions are configurationally stable at-70� and that the configurations of the vinylic sulfides reflect the configurations of the carbanions from which they are derived. It is also concluded that the reactions proceed under orbital control, as this best accounts for the formation of the vinylic sulfides and is in accord with the results of STO-3G calculations carried out on a series of sulfur-bearing allylic carbanions . The likely angle of attack of the carbanions on the enone system is briefly discussed in terms of a published model relating to the attack of a simple nucleophile on an electrophilic double bond.

Intramolecular cyclization of ω-primary amino electrophilic olefins to functionalized pyrrolidines and piperidines.

The intramolecular 1,4-Michael type addition of in situ chemoselectively generated primary amines bearing an electrophilic double bond in the ω position leads to functionalized pyrrolidines and piperidines under very mild conditions.

ChemInform Abstract: Acidic Properties of Compounds with C = C or N = N Electrophilic Double Bonds.

AbstractThe investigation is based on the analysis of the interaction energy of organic compounds, such as (I)‐(IV) e.g., with a selected Lewis basis, obtained via ab initio SCF computations.

On the acidic properties of compounds with CC or NN electrophilic double bonds

Acidic properties of double bonds bearing suitable substituents in symmetrical position are illustrated by theoretical means. The investigation is based on the analysis of the interaction energy of the organic compounds with a selected Lewis basis, obtained via ab initio SCF computations. The stabilizing interaction is essentially electrostatic in nature, and the relative strength of these neutral acids is well correlated with the value of the molecular electrostatic potential. The study is focussed on maleic anhydride (MA) and related compounds, because MA plays an important role in the industrial synthesis of lubricant oil additives (tensioactive dispersants). The autocatalytic role of MA in the condensation reaction with Cl-polyisobutene is illustrated, and other more efficient catalysts are identified using the same theoretical means. Practical rules for the theoretical identification of other possible catalysts are given.

Darstellung von neuen makromolekularen stoffen aus derivaten der 3‐aminocrotonsäure und dimaleinimiden

AbstractCross‐linked polymers are formed by a new addition polymerization of dimaleinimides with bis(3‐aminocrotonic acid)‐esters, ‐amides, or ‐nitriles. Model reactions show that the derivatives of 3‐aminocrotonic acid add to the electrophilic double bond of maleinimide. The resulting succinimid derivatives rearrange thermally to the corresponding pyrrolinones. At higher temperatures, especially in the presence of an excess of maleinimide, a second molecule of maleinimide is added to the pyrrolinone. Some properties of moulded and casted polymers are described.

Stable, nonreducible cross-links of mature collagen

During in vivo maturation, and also during in vitro incubation with physiological buffers, native collagen fibers display a progressive increase in tensile strength and insolubility. Paralleling these physiologically important changes is a progressive loss of the reducible cross-links which initially join the triple-chained subunits of collagen fibers. Although there is evidence suggesting that the reducible cross-links are gradually transformed into more stable, nonreducible cross-links during maturation, the nature of the transformation process and the structure of the stable "mature" cross-links has remained a mystery. In order to test the possibility that cross-link transformation involves addition of a nucleophilic amino acid residue to the reducible cross-links, histidine, arginine, glutamate, aspartate, lysine, and hydroxylysine residues were chemically modified, and the effect of each modification procedure on the in vitro transformation of reducible cross-links was ascertained. The results of these experiments indicated that destruction of histidine, arginine, glutamate, and aspartate residues has no measurable effect on the rate and extent of reducible cross-link transformation in hard tissue collagens. In contrast, modification of lysine and hydrocylysine residues with a wide variety of specific reagents completely blocks the transformation of reducible cross-links. Removal of the reversible blocking groups from lysine and hydroxlylysine residues then allows the transformation to proceed normally. These results indicate that collagen maturation involves nucleophilic addition of lysine and/or hydroxylysine residues to the electrophilic double bond of the reducible cross-links, yielding derivatives which are not only more stable but also capable of cross-linking more collagen molecules than their reducible precursors.

Carbonyl and thiocarbonyl compounds. Part XIV. Reactions of tetrachloro-o-benzoquinone with 3-(2-furyl)- and 3-(2-thienyl)-acrylophenones

Tetrachloro-o-benzoquinone readily undergoes 1,4-cycloaddition with the furyl residue of 3-(2-furyl)acrylophenones to give the 1 : 1 adducts (2). Further addition to the electrophilic double bond of the side chain to give the 2 : 1 adducts (6a–c) requires drastic conditions. In contrast, addition to the side chain of the 3-(2-thienyl)acrylophenones (1d–f) readily gives the 1 : 1 adducts (3a–c), with the thiophen ring unmodified. Adducts (3a–c) form hydrazones and oximes, and the latter react with isocyanates affording oxime carbamates (3k–m) of possible pesticidal importance. The adducts (2a–c) react with benzylmagnesium chloride to give the expected β-benzyl adducts (6a–c), whereas with phenylmagnesium bromide concomitant cleavage of the dioxan ring occurs to give the 3-(2-furyl)-3-phenylpropiophenones (7a–c).

Mature collagen crosslinks

During incubation with physiological buffers at 37°, as well as during in vivo maturation, native collagen fibers display a progressive increase in tensile strength and insolubility. This is paralleled by a progressive loss of reducible, intermolecular crosslinks. The experiments described in this paper indicate that nucleophilic addition of lysine and/or hydroxylysine residues to the electrophilic double bond of the reducible crosslinks transforms them into more stable, non-reducible crosslinks. Indeed, modification of lysine/hydroxylysine residues completely blocks this transformation, while modification of his, arg, glu and asp is without effect. On the basis of these and other experiments, tentative structures are proposed for the stable crosslinks.

Thermolysis of salts of 2-substituted acrylic acids. Novel reduction of a vinyl bromide

Upon heating the sodium or silver salts of 2-chloroacrylic, 2-bromo-3,3-diphenylacrylic, and α-bromofluorenylideneacetic acid alone, in inert solvents, or in olefins, decarboxylation results and, where possible, rearrangement to acetylenes. Similarly, methyl fluorenylideneacetates are demethylated and decarboxylated on heating with sodium iodide. These decompositions do not involve carbenes.Treatment of esters of α-bromofluorenylideneacetic acid with alcoholic alkali or alkoxides causes replacement of bromine by hydrogen, to give fluorenylideneacetic acid in high yield, probably by hydride transfer from the alkoxide ion to the electrophilic double bond.

Enzymatic elimination from a substituted four-carbon amino acid coupled to Michael addition of a beta-carbon to an electrophilic double bond. Structure of the reaction product.

Enzymatic elimination from a substituted four-carbon amino acid coupled to Michael addition of a beta-carbon to an electrophilic double bond. Structure of the reaction product.