Aryl-substituted Alkenes Research Articles

Equilibria and UV-Spectral Characteristics of BrCl, BrCl2−, and Br2Cl− Species in 1,2-Dichloroethane − Stereoselectivity and Kinetics of the Electrophilic Addition of these Species to Alkenes

UV/Vis spectrophotometric measurements have been used to determine the equilibrium constants and the absorption spectra of Bu4N+Br2Cl− and Bu4N+BrCl2− species in 1,2-dichloroethane (DCE) at 25 °C. The formation constants and the absorption spectra of BrCl from Br2 and Cl2 and of Bu4N+Cl3− species from Bu4N+Cl− and Cl2 were also determined in this solvent at 25 °C. The kinetics and the products of bromochlorination of several aryl-substituted olefins with BrCl, with Br2 in the presence of an excess of Bu4N+Cl− (Br2/Cl−), and with BrCl in the presence of an excess of Bu4N+Cl− (BrCl/Cl−) were investigated in DCE at different temperatures. The kinetics and product distribution data for the reactions with Br2/Cl− or BrCl/Cl− are interpreted on the basis of a mechanism involving a product- and rate-determining nucleophilic attack by chloride on the olefin-halogen (Br2 or BrCl) π complex. The data relating to the electrophilic addition of BrCl are interpreted in terms of the initial formation of a 1:1 olefin−BrCl π complex, the ionization of which, catalyzed by a second halogen molecule, gives a bromonium (or β-bromocarbenium) BrCl2− ion pair able to collapse to the corresponding bromochloro adducts. A significant proportion of the ion pair intermediates may, however, actually be present as bromonium (or β-bromocarbenium) Br2Cl− and Br3− ion pairs, and the collapse of these should be responsible for the formation of the dibromides in BrCl addition.

Equilibria and UV-Spectral Characteristics of BrCl, BrCl2−, and Br2Cl− Species in 1,2-Dichloroethane − Stereoselectivity and Kinetics of the Electrophilic Addition of these Species to Alkenes

UV/Vis spectrophotometric measurements have been used to determine the equilibrium constants and the absorption spectra of Bu4N+Br2Cl− and Bu4N+BrCl2− species in 1,2-dichloroethane (DCE) at 25 °C. The formation constants and the absorption spectra of BrCl from Br2 and Cl2 and of Bu4N+Cl3− species from Bu4N+Cl− and Cl2 were also determined in this solvent at 25 °C. The kinetics and the products of bromochlorination of several aryl-substituted olefins with BrCl, with Br2 in the presence of an excess of Bu4N+Cl− (Br2/Cl−), and with BrCl in the presence of an excess of Bu4N+Cl− (BrCl/Cl−) were investigated in DCE at different temperatures. The kinetics and product distribution data for the reactions with Br2/Cl− or BrCl/Cl− are interpreted on the basis of a mechanism involving a product- and rate-determining nucleophilic attack by chloride on the olefin-halogen (Br2 or BrCl) π complex. The data relating to the electrophilic addition of BrCl are interpreted in terms of the initial formation of a 1:1 olefin−BrCl π complex, the ionization of which, catalyzed by a second halogen molecule, gives a bromonium (or β-bromocarbenium) BrCl2− ion pair able to collapse to the corresponding bromochloro adducts. A significant proportion of the ion pair intermediates may, however, actually be present as bromonium (or β-bromocarbenium) Br2Cl− and Br3− ion pairs, and the collapse of these should be responsible for the formation of the dibromides in BrCl addition.

A Cheap, Catalytic, Scalable, and Environmentally Benign Method for Alkene Epoxidations

A Cheap, Catalytic, Scalable, and Environmentally Benign Method for Alkene Epoxidations

Asymmetric hydroformylation catalyzed by rhodium(I) complexes of novel chiral spiro ligands

Chiral diphosphites and phosphinite-phosphites derived from spiro[4.4]nonane-1,6-diol were synthesized. Using Rh[I]– 7 complex in asymmetric hydroformylation of styrene, high regioselectivity (97%) and moderate enantioselectivity (65% ee) have been obtained. This catalyst system was also effective for aryl-substituted olefins. The diphosphites 8 and 9 bearing 1,1′-binaphthyl backbones were tested and the opposite configuration of the product indicates that the sense of enantioface selection is mainly dictated by the configuration of the terminal groups. Phosphinite–phosphite ligands gave low enantiomeric excesses (up to 48% ee) and low b/ n ratios. These results suggest that the regio- and enantioselectivity is mainly affected by the bulky substituents on terminal groups. The crystal structure of Rh( 7)(acac) are presented. The distortion in the structure is indicative of a crowded rhodium center.

Enantioselective Hydrogenation of Olefins with Iridium-Phosphanodihydrooxazole Catalysts.

High turnover numbers and up to 98% ee were obtained in the catalytic hydrogenation of unfunctionalized aryl-substituted olefins with iridium-phosphanyldihydrooxazole complexes 1 (see reaction scheme). The anion of the complex-for example, hexafluorophosphate or tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF- )-has a remarkable effect on the reactivity and longevity of the catalyst.

Side chain oxidation of aromatic compounds by fungi. 7. A rationale for sulfoxidation, benzylic hydroxylation, and olefin oxidation by Mortierella isabellina

The fungus Mortierella isabellina ATCC 42613 catalyses the biotransformation of substituted-aryl methyl sulfides to give sulfoxides of predominantly ( R) configuration; of aryl-substituted alkenes to give chiral vicinal diols; and of various phenylalkanes and phenylcycloalkanes to give ( R)-configuration benzylic alcohols. The nature of the products from all these processes may be accounted for by a single model based on restrictive space descriptors that can be used to rationalise these reactions, and which is proposed as a predictor of the outcome of the M. isabellina-catalyzed oxidations of similar substrates.

Synthesis and catalytic reactivity of sterically and electronically modified D 4-symmetric metallotetraarylporphyrins

Two new sterically-modified and two electronically-modified D 4-symmetrical tetraarylporphyrin ligands have been prepared and the catalytic activity of their manganese complexes in epoxidations of aryl-substituted alkenes studied. Moderate reactivity changes were observed in catalytic epoxdiations with these electronically varied tetraaarylporphyrin complexes, the methoxy derivative giving slightly improved selectivity (83% e.e. with cis-β-methylstyrene).

Attachment of a styryl group to the 6-position of a protected penicillanic acid via cobaloxime-mediated radical alkyl-alkenyl cross coupling

Cobaloxime-catalyzed cross coupling of styrene with 6α-bromopenicillanic acid pivalolyl-oxymethyl ester ( 4) introduces a styryl group into the 6 position of the penicillanic acid nucleus. The method should be capable of introducing a variety of aryl-substituted alkenes into the 6 position. Such compounds may be useful as novel β-lactam antibiotics/β-lactamase inhibitors.

Palladium-Catalyzed Cross-Coupling of Organoboron Compounds with Iodonium Salts and Iodanes.

The palladium-catalyzed cross-coupling reaction of iodinanes (iodonium salts and iodanes) with organoboron compounds to form carbon-carbon bonds was achieved at ambient temperature under aqueous conditions in the absence of base. Coupling of phenylboronic acid with diphenyliodonium tetrafluoroborate in the presence of Pd(PPh(3))(4) (0.2 mol %) or Pd(OAc)(2) (0.2 mol %) under aqueous conditions gave biphenyl in almost quantitative yield. Under the same conditions, substituted boronic acids, boronates, and trialkylboranes were readily coupled with diaryl-, alkenyl-, and alkynyliodonium salts. Finally, the iodanes ArI(OH)OTs underwent cross-coupling with boronic acids, boronates, and trialkylboranes to afford biphenyls and aryl-substituted alkenes.

Palladium-catalyzed cross-coupling of aryl and alkenyl boronic acids with alkenes via oxidative addition of a carbonboron bond to palladium(O)

Arylboronic acids react with alkenes in acetic acid at 25°C in the presence of a catalytic amount of palladium(II) acetate together with sodium acetate to give the corresponding aryl-substituted alkenes in high yields. Alkenylboronic acids react with alkenes under similar conditions to give the corresponding conjugated dienes stereospecifically, but the product yields are lower, compared with those from arylboronic acids. Similar treatment of sodium tetraphenylborate (NaBPh 4) with alkenes also affords the corresponding phenylated alkenes in high yields together with biphenyl and benzene as side products. Oxidative addition of a carbonboron bond to palladium(O), formed in situ, to give an organopalladium(II) species is assumed to be the key step of these cross-coupling reactions.

Production of chiral epoxides by an ethene-utilisingMicrococcus sp.

An ethene-utilising bacterium was isolated in pure culture from soil and was tentatively identified as aMicrococcus sp. The organism accumulated epoxyalkanes (0.2–13 mM) from internal, terminal, cyclic and aryl-substituted olefins and exhibited a substrate specificity which was different from that expected on the basis of the chemical reactivity pattern in peracid epoxidations. Epoxyalkanes were hydrolysed at a much slower rate than the epoxidation step which allowed them to accumulate. Ethene-grown cells catalysed the stereospecific formation of R-1,2-epoxypropane (enantiomeric excess: e.e.=96%), R-1,2-epoxybutane (e.e.=94%) andtrans-(2R,3R)-epoxybutane (e.e.=84%). An ethene monooxygenase was implicated in the production of chiral epoxides in cell-free extracts of the bacterium. The (2S,3S)-enantiomer of racemictrans-2,3-epoxybutane was stereoselectively hydrolysed to completion resulting in an enrichment in the (2R,3R)-enantiomer. Further hydrolysis of 1,2-epoxyalkanes (C3-C4), however, occurred via complete destruction of both stereoisomers.

Photoinduced Nucleophilic Addition of Ammonia and Alkylamines to Aryl-Substituted Alkenes in the Presence of p-Dicyanobenzene

Abstract The photoamination of 1,1-diphenylpropene (1a) with ammonia and some primary alkylamines in the presence of p-dicyanobenzene gave the corresponding N-substituted 2-amino-1,1-diphenylpropane (2a–e) along with the formation of 3-methyl-4,4-diphenylbutanenitrile (3a), 1,1-diphenylpropane (4a), 3,3-diphenylpropene (5), and diphenylmethane (6). In the case of 1,1-diphenylethene (1b), N-substituted 1-amino-2,2-diphenylethane (2f–h), 4,4-diphenylbutanenitrile (3b), and 1,1-diphenylethane (4b) were produced. In photoamination with t-butylamine in acetonitrile, 3a and 3b were mainly formed as a consequence of the incorporation of acetonitrile to 1a and 1b. The photoamination of 1-phenyl-3,4-dihydronaphthalene (1c) with isopropylamine or t-butylamine gave cis- and trans-N-substituted 1-phenyl-2-amino-1,2,3,4-tetrahydronaphthalenes (15 and 16) in a ratio of ca. 8:2. The mechanism of photoamination is discussed in terms of a photochemical electron transfer of 1 to p-dicyanobenzene followed by a nucleophilic addition of the amine to the cation radical of 1.

Alkene formation through condensation of phenylmethanesulphonyl fluoride with carbonyl compounds

Arylmethanesulphonyl fluorides condense with aromatic, aliphatic and conjugated aldehydes and ketones in the presence of potassium carbonate and a crown ether to give aryl-substituted alkenes in satisfactory to modest yields.

Reactivity of (C5Me5)2Sm with aryl-substituted alkenes: synthesis and structure of a bimetallic styrene complex that contains an .eta.2-arene lanthanide interaction

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReactivity of (C5Me5)2Sm with aryl-substituted alkenes: synthesis and structure of a bimetallic styrene complex that contains an .eta.2-arene lanthanide interactionWilliam J. Evans, Tamara A. Ulibarri, and Joseph W. ZillerCite this: J. Am. Chem. Soc. 1990, 112, 1, 219–223Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://doi.org/10.1021/ja00157a035RIGHTS & PERMISSIONSArticle Views407Altmetric-Citations120LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (757 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Reactions of azo and azoxy sulphones with transition metal complexes. Part 7. Arylation of olefins with arylazoxy aryl sulphones catalysed by a palladium(0) phosphine complex

The arylation of acyclic and cyclic olefins by arylazoxy aryl sulphones has been investigated in the presence of a palladium(0) catalyst in benzene. Both of the aryl groups of the arylazoxy aryl sulphones are found to participate in the arylation. Two equivalents of aryl-substituted olefins were obtained when the reactions were carried out at 80 °C, whereas one equivalent of olefin was arylated at 120 °C. A plausible catalytic cycle involving a diarylpalladium(II) species is proposed.

Arylation of Olefins by Arylazo Aryl Sulfones under Palladium(0) Catalysis

Abstract The palladium(0)-catalyzed reaction of arylazo aryl sulfones with olefins in benzene at 80°C gave aryl-substituted olefins in good yield. Diarylpalladium(II) species was proposed as an intermediate in this reaction.

Mechanistic studies of alkene epoxidation catalyzed by nickel(II) cyclam complexes. Oxygen-18 labeling and substituent effects

The oxidations of cyclohexene and various aryl-substituted alkenes are catalyzed by the cyclam (1,4,8,11-tetraazacyclotetradecane) complex of Ni(NO/sub 3/)/sub 2/ with iodosylbenzene as terminal oxidant. Epoxides are the major products; however, small amounts of ring-opened products, over-oxidation to ketones or aldehydes, and allylic oxidation of cyclohexene are also observed. E olefins are more reactive than the corresponding Z olefins in contrast to the results of iron porphyrin catalysis, and kinetic studies of para-substituted styrenes indicate that the reaction is facilitated by electron-donating substituents. Labeling studies with PhI/sup 18/O confirm that the epoxide oxygen is derived from PhIO while allylic oxidation and over-oxidation products involve both PhIO and exogenous sources of oxygen. A pericyclic mechanism for the formation of PhCHO is proposed along with the intermediacy of a high-valent nickel-oxo complex as the active oxidant. These results are discussed in light related transition-metal/PhIO oxidation mechanisms.

Cycloaddition Reactions of Highly Stabilized Isoquinolinium Methylides to Nonactivated Olefins and Electron-Rich Olefins

Abstract Highly stabilized isoquinolinium methylides bearing two electron-withdrawing substituents at the ylide carbon undergo cycloadditions with aryl-substituted olefins (acenaphthylene, (E)- and (Z)-stilbenes, indene, and styrene), alkyl-substituted olefins (norbornene, (Z)-3-hexene-1,6-dinitrile, 1-hexene, 2-propen-1-ol, and 3-(trimethylsilyloxy)propene), and electron-rich olefins (vinylene carbonate, butyl vinyl ether, and phenyl vinyl sulfide). These cycloadditions proceed in an exclusively regioselective and mostly stereoselective manner.

Asymmetric Dihydroxylation Of Olefins Achieved

When K. Barry Sharpless invented asymmetric epoxidation in 1980, organic chemists hailed it as the reaction of the decade. Now in a preliminary announcement of catalytic asymmetric dihydroxylation of olefins, the Massachusetts Institute of Technology chemistry professor seems to have gotten an early start on the next decade [ J. Am. Chem. Soc. , 110 , 1968 (1988)]. There is still a lot of work ahead to perfect the new reaction. So far, only aryl-substituted olefins give good results. But the technique is so widely useful and early efforts as optimization so successful that it seems likely the technique will play important roles in large-scale pharmaceutical production as well as in academic natural product synthesis. Like the earlier epoxidation, the new dihydroxylation installs asymmetric configurations at two carbon atoms at once. Also as with the epoxidation, chemists apparently can dictate which enantiomer or diastereoisomer will result. The epoxidation needs allylic alcohols as substrates, but the di...

Cobalt-catalyzed reaction of nitric oxide with aryl-substituted olefins in the presence of tetrahydroborate ion

Cobalt-catalyzed reaction of nitric oxide with aryl-substituted olefins in the presence of tetrahydroborate ion