Carbonyl Olefination Research Articles

Intramolecular carbonyl olefination of esters. Regioselective preparation of enol ethers of cyclic ketones by the titanocene(ii)-promoted reaction of alkyl ω,ω-bis(phenylthio)alkanoates

The treatment of alkyl ω,ω-bis(phenylthio)alkanoates with Cp2Ti[P(OEt)3]2 produced enol ethers of 5-, 6-, 7-, and 9-membered cyclic ketones.

Speciation and kinetics related to catalytic carbonylation in the presence of cis-[Ir(CO)2I2]P(C6H5)4 under CO and H2 pressures.

The differences in the reactivities of the square-planar complexes cis-[Rh(CO)2I2]- (1) and cis-[Ir(CO)2I2]- (2), involved in the catalytic carbonylation of olefins, are investigated, with P(C6H5)4+ as the counterion, by ambient- and high-pressure NMR and IR spectroscopy. Under an elevated pressure of CO, 1 and 2 form the [M(CO)3I] complexes with the equilibrium constants KIr approximately 1.8 x 10(-3) and KRh approximately 4 x 10(-5). The ratio KIr/KRh close to 50 shows that, under catalytic conditions (a few megapascals), only complex 1 remains in the anionic form, while a major amount of the iridium analogue 2 is converted to a neutral species. The oxidative addition reactions of HI with 1 and 2 give two monohydrides of different geometries, mer,trans-[HRh(CO)2I3]- (3) and fac,cis-[HIr(CO)2I3]- (4), respectively. Both hydrides are unstable at ambient temperature and form, within minutes for Rh and within hours for Ir, the corresponding cis-[M(CO)2I2]- (1 or 2) and [M(CO)2I4]- (5 or 6) species and H2. When an H2 pressure of 5.5 MPa is applied to a nitromethane solution of complex 2, ca. 50% of 2 is transformed to cis-dihydride complexes. The formation of cis,cis,cis-[IrH2(CO)2I2]- (8a) is followed by intermolecular rearrangements to form cis,trans,cis-[IrH2(CO)2I2]- (8b) and cis,cis,trans-[IrH2(CO)2I2]- (8c). A small amount of a dinuclear species, [Ir2H(CO)4I4]x- (9), is also observed. The formation rate constants for 8a and 8b at 262 K are k1(262) = (4.42 +/- 0.18) x 10(-4) M-1 s-1, k-1(262) = (1.49 +/- 0.07) x 10(-4) s-1, k2(262) = (2.81 +/- 0.04) x 10(-5) s-1, and k-2(262) = (5.47 +/- 0.16) x 10(-6) s-1. The two equilibrium constants K1(262) = [8a]/([2][H2]) = 2.97 +/- 0.03 M-1 and K2(262) = [8b]/[8a] = 5.13 +/- 0.10 show that complex 8b is the thermodynamically stable addition product. However, no similar H2 addition products of the rhodium analogue 1 are observed. The pressurization with H2 of a solution containing 2 and 6 give the monohydride 4, the dihydrides 8a and 8b, the dinuclear complex 9, and the two new complexes [Ir(CO)2I3] (10) and [HIr(CO)2I2] (11). The reactions of the iridium complexes with H2 and HI are summarized in a single scheme.

Applications of Olefination Reactions to Cassiol Synthesis

first_page settings Order Article Reprints Font Type: Arial Georgia Verdana Font Size: Aa Aa Aa Line Spacing:    Column Width:    Background: Open AccessAbstract Applications of Olefination Reactions to Cassiol Synthesis by María I. Colombo, Jose A. Bacigaluppo, Mirta P. Mischne, Juán Zinczuk and Edmundo A. Rúveda Instituto de Química Orgánica de Síntesis (IQUIOS-UNR) Casilla de Correo 991, 2000 Rosario, Argentina Molecules 2000, 5(3), 327-329; https://doi.org/10.3390/50300327 Published: 22 March 2000 Download Download PDF Download PDF with Cover Download XML Download Epub Versions Notes Abstract: Olefination reactions directed to the synthesis of cassiol from compounds 2-5 will be discussed. IntroductionCassiol (1), which exhibits a potent antiulcer activity, contains a functionalized cyclohexenone mo-eity with a quaternary stereogenic center at C-4 and a 2-vinyl-1,3-diol chain, which is connected at the C-3 position. Because of its structural features and pharmacological activity, a number of synthesis have been recorded [1]. Our approach toward the synthesis of 1 involves the C-1’- C-2’ double bond disconnection through a carbonyl olefination procedure [2]. This sequence allow us to explore the ole-fination reaction in two differents ways, switching the polarity of the coupling partners as shown in the following scheme.By following approach a, a precursor of cassiol (1) was obtained in our laboratory, but unfortu-nately in an unsatisfactory low yield [3]. In order to improve the yield of the coupling reaction, com-pounds 2-5 were then selected for study. ExperimentalCompounds 2-5 were prepared according to standard methods. DiscussionDue to lack of success in the coupling of 4-5 with 2 and 3 by using differents conditions of solvents and bases we turned our attention to approach b.Starting with compound 4, the diol 6 has been ob-tained. Treatment of 6 with mercaptobenzothiazole provided the corresponding sulfide 7. Starting with 7 and through the corresponding sulfone 8 we hope to improve the yield of the coupling product, on the basis of the recent report of Hart and Kozikowski et al [4]. AcknowledgementsUNR, CONICET, Agencia Nacional de Promoción Cinentífica.References and NotesColombo, M.I.; Rúveda, E.A. J. Braz. Chem. Soc. 1998, 9, 303. [CrossRef] Entwistle, D. Contemporary Organic Synthesis 1997, 4, 40. Colombo, M.I.; Bacigaluppo, J.A.; Rúveda, E.A. An. Asoc. Quim. Argent. 1998, 86, 312. Hart, D.J.; Li, J.; Wu, W-L.; Kozikowski, A.P. J. Org. Chem. 1997, 62, 5023. [CrossRef] Share and Cite MDPI and ACS Style Colombo, M.I.; Bacigaluppo, J.A.; Mischne, M.P.; Zinczuk, J.; Rúveda, E.A. Applications of Olefination Reactions to Cassiol Synthesis. Molecules 2000, 5, 327-329. https://doi.org/10.3390/50300327 AMA Style Colombo MI, Bacigaluppo JA, Mischne MP, Zinczuk J, Rúveda EA. Applications of Olefination Reactions to Cassiol Synthesis. Molecules. 2000; 5(3):327-329. https://doi.org/10.3390/50300327 Chicago/Turabian Style Colombo, María I., Jose A. Bacigaluppo, Mirta P. Mischne, Juán Zinczuk, and Edmundo A. Rúveda. 2000. "Applications of Olefination Reactions to Cassiol Synthesis" Molecules 5, no. 3: 327-329. https://doi.org/10.3390/50300327 Find Other Styles Article Metrics No No Article Access Statistics For more information on the journal statistics, click here. Multiple requests from the same IP address are counted as one view.

Nuclear magnetic resonance spectra and structure of fluorinated oxetanes

Fluorine, hydrogen, and carbon-13 nuclear magnetic resonance spectral data are reported for a variety of oxetane compounds containing fluorine on or near the ring. Effects of substituents on the spectra are analyzed and correlations of chemical shifts and coupling constants in terms of molecular structure are presented. Application of NMR permits the assignment of the regiochemistry and stereochemistry of the products of photochemical reactions between carbonyl compounds and olefins. Steric interactions and possible deviations from ring planarity are discussed in relation to the pathways of nuclear spin–spin interaction and to the trends observed in NMR parameters.

Synthesis of carbocycles and heterocycles by the titanocene(II)-promoted reactions of thioacetals

The preparation of carbocyclic and heterocyclic compounds by the low-valent titanium species-promoted intramolecular reactions of thioacetals was studied. The cyclization of thioacetals having an olefin moiety proceeded with the loss of terminal olefin carbon to produce the corresponding five-, six-, and seven-membered cycloalkenes when they were treated with the low-valent titanium species Cp 2Ti[P(OEt) 3] 2. This method has been successfully applied to the syntheses of cyclic unsaturated amines and ethers. When S-[3,3-bis(phenylthio)propyl] thioalkanoates were treated with the low-valent titanium species, the intramolecular carbonyl olefination proceeded to produce 5-substituted 2,3-dihydrothiophenes.

A new rhodium catalyst: formation of

A new rhodium catalyst: formation of

Organopalladium chemistry in the '60s and '70s

The history of organopalladium chemistry in the 1960s–1970s is briefly outlined. Organopalladium chemistry has a 40 year history. It was born in the late 1950s with the invention of the Wacker process. Inspired by the Wacker reaction, we started our research on Pd chemistry in the early 1960s and discovered the reaction of the PdCl2 complex of COD (cyclooctadiene) with carbonucleophiles, which was the first example of carbon–carbon bond formation by means of a Pd complex. Then we opened the new field of π-allylpalladium chemistry by discovering the reaction of π-allylpalladium chloride with carbonucleophiles. Oxidative carbonylation of alkenes and alkynes mediated by Pd(II) and hydrocarbonylation of alkenes and alkynes catalyzed by Pd(0) were other discoveries made in our laboratory. An account of the development of organopalladium chemistry in our laboratory in the 1960s is presented. In addition, major accomplishments in organopalladium chemistry reported by other groups in the 1960s and 1970s are summarized.

Novel palladium(II) complex containing a chelating anionic N-O ligand: efficient carbonylation catalyst

[reaction: see text] A novel palladium(II) complex containing chelating anionic pyridine-2-carboxylato and labile tosylato ligands is a highly efficient catalyst for the carbonylation of organic alcohols and olefins to carboxylic acids/esters. Carbonylation of primary, secondary, and tertiary alcohols as well as linear and functionalized terminal olefins was studied. In all cases remarkable activity and selectivity were observed. The catalyst is stable under reaction conditions even in the absence of excess phosphine ligands.

Palladium(I) Carbonyl Cation-Catalyzed Carbonylation of Olefins and Alcohols in Concentrated Sulfuric Acid

A new palladium catalyst was found to exhibit high catalytic activity for carbonylation of olefins and alcohols. cyclo-Bis(μ-carbonyl)dipalladium(I) cation (1) with bridging CO ligands is formed by reductive carbonylation of palladium sulfate, PdSO4, in concentrated H2SO4. When an olefin or alcohol is added, complex 1 changes to a new complex (2) with terminal CO ligands, and tertiary carboxylic acids are obtained in high yields at room temperature and atmospheric pressure of CO. IR and 13C NMR studies suggest that complex 2 may be tentatively formulated to be [Pd2(CO)2]2+, in which the terminal CO ligands are chemically equivalent. Complex 1 is a catalyst precursor, and complex 2 functions as an active species for the carbonylation of olefins and alcohols. The catalytic behavior of the palladium carbonyl catalyst supports the recently proposed reaction mechanism involving an olefin−metal−CO complex as an intermediate for the catalytic carbonylation of olefins and alcohols in strongly acidic solution.

Advances in transition-metal catalyzed hydroxycarbonylation reactions in aqueous-organic two-phase system

A survey of the literature related to the aqueous organometallic chemistry and catalysis shows that the interest in the carbonylation reactions in two-phase systems has remarkably grown during the five last years and that most of carbonylation reactions conducted in homogeneous medium, i.e., the carbonylation of benzyl chloride, bromobenzene, allylic halides, phenethylbromide and olefins have been successfully applied under biphasic conditions. With allylic halides and benzyl alcohol, the catalytic activities appear even much higher than those obtained in homogeneous systems. Nevertheless the lack of stability of palladium–water soluble phosphine based catalyst often observed limits its reuse and constitutes at the present the major drawback of these processes.

Synthesis of aminomethyl substituted silacyclohexanes from divinylsilanes: An unusually selective [formula omitted] sequence

The preparation of aminomethyl substituted silacyclohexane derivatives starting from divinylsilanes and secondary amines is achieved in a selective one-pot tandem hydroformylation condensation sequence starting with a double olefin carbonylation and proceeding with an enamine generation followed by an aldol condensation step. Final hydrogenation leads to the silacycle in medium up to quantitative yields.

Sodium and Potassium Derivatives of 2-(Diphenylphosphinoyl)-2-Phenyl-Ethenol: Synthesis, Structure and Reactivity

The sodium and potassium derivatives of 2-(diphenylphosphinoyl)-2-phenylethenol (2 and 3, respectively) are obtained and their (E)-enolate structure is proved by spectroscopic methods. The study of their reactivity shows that regiospecific O-acylation of 2 and O-alkylation of 3 takes place, the corresponding 1-acetoxy-2-(diphenylphosphinoyl)-2-phenyl-ethene 4 and 1-benzyloxy-2-(diphenylphosphinoyl)-2-phenyl-ethene 5 is isolated. The reaction of carbonyl olefination is not observed.

Carbonyl Olefination by Means of a gem-Dichloride-Cp(2)Ti[P(OEt)(3)](2) System.

The preparation of highly substituted olefins by carbonyl olefination using a gem-dichloride-Cp(2)Ti[P(OEt)(3)](2) system was studied. The treatment of organotitanium species, formed by reaction with titanocene(II) species from gem-dichlorides having two alkyl substituents, with an aldehyde or ketone afforded tri- or tetrasubstituted olefins in good yields. Acyclic or cyclic trisubstituted vinyl ethers were also obtained by a similar reaction using carboxylic esters or lactones as carbonyl components.

Some recent applications of olefin metathesis in organic synthesis: A review

A review is given of a selection of papers published in the past year in this rapidly expanding field. Such papers may be divided into four groups: (i) those in which ring-closing metathesis (RCM) has been used as a key step in the total synthesis of a natural product: ( R)-(+)-lasiodiplodin, dactylol, (−)-stemoamide, and epothilone A; (ii) those in which RCM has been used to make a sub-unit of a natural product: the marine toxins brevetoxin B, brevetoxin A, and maitotoxin; (iii) those in which RCM has been used to make compounds of known biological activity: fluvirucin B 1 (Sch 38516); (iv) those in which metathesis reactions have been used to make compounds of potential synthetic importance: crown ethers, aza sugars (polyhydroxylated pyrrolidines), β-lactams, chromenes, and aminoacids. The catalysts used have been one of the following four metal carbene complexes: the Schrock catalyst Mo(CHCMe 2Ph)(NC 6H 3-2,6- i-Pr 2)[OCMe(CF 3) 2] 2; the Grubbs catalysts Ru(CHCHCPh 2)Cl 2(PCy 3) 2 and Ru(CHPh)Cl 2(PCy 3) 2, where Cy=cyclohexyl; and the Tebbe reagent which behaves as Ti(CH 2)Cp 2, where Cp=cyclopentadienyl. In this paper these are denoted by Mo-1, Ru-1, Ru-2, and Ti-1, respectively. Ti-1 is especially useful for effecting RCM by the carbonyl–olefination reaction, while the RCM of enynes, catalyzed by Ru-2, is another valuable metathesis reaction.

ChemInform Abstract: Dithioacetals as an Entry to Titanium—Alkylidene Chemistry: A New and Efficient Carbonyl Olefination

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.

Selective hydroboration of alkenes and alkynes in the presence of aldehydes and ketones

The reactions of terminal alkenes in the presence of ketones or aldehydes with a variety of borane reagents have been investigated. It was found that the selective hydroboration of a terminal alkene in the presence of a ketone or an aldehyde is most efficient when dicyclohexylborane is used as the hydroborating agent. The hydroboration of olefinic ketones and olefinic aldehydes with dicyclohexylborane generates the corresponding hydroxyaldehydes and hydroxyketones in good yields after oxidation with sodium perborate. The hydroboration of alkynyl ketones and alkynyl aldehydes with dicyclohexylborane yields the corresponding olefinic carbonyl compounds after protonation, or dicarbonyl compounds after oxidation.Key words: hydroboration, reduction, dicyclohexylborane, hydroxyaldehyde, hydroxyketone.

Dithioacetals as an Entry to Titanium-Alkylidene Chemistry: A New and Efficient Carbonyl Olefination.

Wittig, Horner-Wadsworth-Emmons, Julia-Lythgoe, Tebbe, Grubbs, and Petasis-when it comes to carbonyl olefinations, these names are familiar to all chemistry students. In the future, the name Takeda will probably have to be added to this list. His recent work on the formation of titanium-alkylidene species from dithioacetals has provided organic chemists with a remarkable method for carbonyl olefination that is generally applicable under neutral to Lewis acidic conditions.

Dithioacetals as an Entry to Titanium–Alkylidene Chemistry: A New and Efficient Carbonyl Olefination

Dithioacetals as an Entry to Titanium–Alkylidene Chemistry: A New and Efficient Carbonyl Olefination

The CoCl 2/Ph(Et) 2N:BH 3/CO system: Reactions of the borane and cobalt carbonyl species

The CoCl 2/Ph(Et) 2N:BH 3/CO system is useful for the hydroboration and carbonylation of alkenes to obtain the corresponding dialkyl ketones. The cobalt carbonyl species formed in situ in this way is also useful for hydroacylation–cyclisation of norbornene and for the Pauson–Khand reaction.

ChemInform Abstract: Olefin Carbonylation Catalysis with Cationic Palladium Complexes: Selectivity and Possible Intermediates

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.