- Palladium-catalyzed tandem oxidative cyclization of 1-bromohexa-1,5-dien-3- ols: Easy access to cyclopentenones
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The novel Pd-catalyzed tandem cyclization of 1-bromohexa-1,5-dien-3-ols, prepared from the corresponding β-bromo-vinylaldehydes to cyclopentenone derivatives has been developed.
- Mal, Sajal Kanti,Ray, Devalina,Ray, Jayanta K.
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- Silacycle-Templated Intramolecular Diels-Alder Cyclizations for the Diastereoselective Construction of Complex Carbon Skeletons
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The utility of the dioxasiline ring as a π-facial directing group in the intramolecular Diels-Alder cyclization is explored. An initial investigation of substrate scope demonstrates that the rigidity of this directing group delivers robust stereocontrol across a number of substrates, affording single diastereomers in moderate to good yields. A mechanistic investigation reveals that the reactive diene is formed through γdeprotonation followed by [1,5] hydride shifts.
- Carlson, Paul R.,Burns, Alexander S.,Shimizu, Emily A.,Wang, Shilin,Rychnovsky, Scott D.
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- Palladium-catalyzed novel cycloisomerization: An unprecedented domino oxidative cyclization towards substituted carbocycles
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Efficient Pd-catalyzed cyclization of homoallylated β-bromo- vinylalcohols via a domino process to carbocycle derivatives in presence of different bases is reported. An unexpected and novel palladium-mediated Heck-type intramolecular oxidative cyclization
- Ray, Devalina,Mal, Sajal K.,Ray, Jayanta K.
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- Synthesis and properties of novel substituted 4,5,6,7-tetrahydroindenes and selected metal complexes
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The synthesis of a complete series of substituted 4,5,6,7-tetrahydroindenes (4,5,6,7-tetrahydroindene, 1; 1-methyl-, 1,3-dimethyl- and 1,2,3-trimethyl-4,5,6,7-tetrahydroindene, 2-4) is reported.The synthesis of ferrocenes (8-11) from these substituted cyclopentadienes is described.The electrochemistry of these ferrocenes indicates that these complexes are more readily oxidized than ferrocene and that the effect of methyl or alkyl substituents on the ease of oxidation is additive.A single crystal X-ray structure of two of the ferrocenes, bis(1,3-dimethyl-4,5,6,7-tetrahydroindenyl)iron(II), 10, and bis(1,2,3-trimethyl-4,5,6,7-tetrahydroindenyl)iron(II), 11, indicates that steric hindrance causes the alkyl substituents to be bent away from the plane of the cyclopentadienyl ring.However, the structures differ in that the cyclopentadienyl rings in 10 are staggered whereas those in 11 are eclipsed.The synthesis of the cyclopentadienyltricarbonylmethyl compounds of molybdenum and tungsten from 3 and 4 is also described.Keywords: Iron; Molybdenum; Tungsten; Indenes; Metallocenes; Electrochemistry
- Austin, Rachel N.,Clark, T. Jeffrey,Dickson, Thomas E.,Killian, Christopher M.,Nile, Terence A.,et al.
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- Vinylsilane mediated regiospecific cyclopentenone annulation of ketones
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The development of a new cyclopentenone annulation sequence of general scope which involves Friedel-Crafts acylation of a vinylsilane with an α,β-unsaturated acid chloride followed by Nazarov cyclization is reported.
- Fristad, William E.,Dime, David S.,Thomas R, Bailey,Leo A, Paquette
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- SYNTHESIS OF SUBSTITUTED CYCLOPENTADIENE COMPOUNDS AND METALLOCENES
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A method of synthesizing a substituted cyclopentadiene compound. The synthesis comprises a step of cyclizing, in the presence of a phosphorous pentoxide/methanesulfonic acid reagent, an alpha,beta-unsaturated carboxylic acid, cycloalkyl ester compound to
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Paragraph 0059
(2020/05/13)
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- SYNTHESIS OF CYCLOPENTENONES
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A method comprising synthesizing a substituted cyclopentenone compound via reaction of a substituted cycloalkyl acrylate ester in the presence of phosphorous pentoxide/methanesulfonic acid reagent to make the substituted cyclopentenone compound.
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Paragraph 0046
(2020/05/13)
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- SYNTHESIS OF CYCLIC ORGANIC COMPOUNDS AND METALLOCENES
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A method comprising synthesizing a cyclic organic compound via reaction of an unsubstituted or substituted cyclohexene with an unsubstituted or substituted acrylic acid in the presence of phosphoric and/or sulfonic acid reagent to make the cyclic organic compound. Also, a method of synthesizing a ligand for a transition metal, and a related substituted ligand-metal complex and catalyst, from the unsubstituted or substituted cyclohexene and unsubstituted or substituted acrylic acid. Also, the cyclic organic compound, ligand, and substituted ligand-metal complex and catalyst synthesized thereby. Also a method of polymerizing an olefin with the catalyst to give a polyolefin, and the polyolefin made thereby.
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Paragraph 0070; 0071
(2019/04/26)
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- Correlating reactivity and selectivity to cyclopentadienyl ligand properties in Rh(III)-catalyzed C-H activation reactions: An experimental and computational study
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CpxRh(III)-catalyzed C-H functionalization reactions are a proven method for the efficient assembly of small molecules. However, rationalization of the effects of cyclopentadienyl (Cpx) ligand structure on reaction rate and selectivity has been viewed as a black box, and a truly systematic study is lacking. Consequently, predicting the outcomes of these reactions is challenging because subtle variations in ligand structure can cause notable changes in reaction behavior. A predictive tool is, nonetheless, of considerable value to the community as it would greatly accelerate reaction development. Designing a data set in which the steric and electronic properties of the CpxRh(III) catalysts were systematically varied allowed us to apply multivariate linear regression algorithms to establish correlations between these catalyst-based descriptors and the regio-, diastereoselectivity, and rate of model reactions. This, in turn, led to the development of quantitative predictive models that describe catalyst performance. Our newly described cone angles and Sterimol parameters for Cpx ligands served as highly correlative steric descriptors in the regression models. Through rational design of training and validation sets, key diastereoselectivity outliers were identified. Computations reveal the origins of the outstanding stereoinduction displayed by these outliers. The results are consistent with partial η5-η3 ligand slippage that occurs in the transition state of the selectivity-determining step. In addition to the instructive value of our study, we believe that the insights gained are transposable to other group 9 transition metals and pave the way toward rational design of C-H functionalization catalysts.
- Piou, Tiffany,Romanov-Michailidis, Fedor,Romanova-Michaelides, Maria,Jackson, Kelvin E.,Semakul, Natthawat,Taggart, Trevor D.,Newell, Brian S.,Rithner, Christopher D.,Paton, Robert S.,Rovis, Tomislav
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supporting information
p. 1296 - 1310
(2017/05/16)
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- Palladium-catalyzed intramolecular oxidative heck cyclization and its application toward a synthesis of (±)-β-cuparenone derivatives supported by computational studies
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A novel and efficient intramolecular oxidative cyclization of substituted homoallylic alcohols to form cyclic keto compounds under palladium-catalyzed conditions is described. The reaction has practical applications in the synthesis of sesquiterpenes. The
- Ray, Devalina,Nasima, Yasmin,Sajal, Mal K.,Ray, Priyanka,Urinda, Sharmistha,Anoop, Anakuthil,Ray, Jayanta K.
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p. 1261 - 1269
(2013/07/19)
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- New Synthetic Approach to Cyclopenta-Fused Heterocycles Based upon a Mild Nazarov Reaction
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The Pd-catalyzed coupling reaction of lactam or lactone-derived vinyl triflates and phosphates with α-alkoxydienylboronates gives conjugated alkoxytrienes in which one of the double bonds is embedded in a heterocyclic moiety. If subjected to mild acidic hydrolysis, these compounds undergo a 4π electrocyclization process (Nazarov reaction) which furnishes cyclopenta-fused O- and N-heterocycles in good yields. The scope of the work has been that of closely examining the role and effect of both the heteroatom and the heterocycle ring size on the outcome of the electrocyclization, as well as the torquoselectivity of this process. The presence of the heteroatom was essential in stabilizing the oxyallyl cation intermediate, thus allowing the reaction to occur. The ring size was also a basic parameter in the cyclization step: five-membered azacycles required more drastic conditions to give 5-5 fused systems and did so only after an initial hydrolysis to the corresponding divinyl ketones. As for the torquoselectivity, with both 2-methyl and 4-methyl substituted lactam derivatives steric interactions seem to have a role in forcing the conrotatory process to take place in one sense only: allowing the synthesis of diastereomerically pure compounds to be realized. Because different patterns of substitution on the heterocycle are compatible with the reaction conditions, the methodology developed could be very useful for the synthesis of natural products and biologically active compounds containing cyclopenta-fused O- and N-heterocycle moieties.
- Occhiato, Ernesto G.,Prandi, Cristina,Ferrali, Alessandro,Guarna, Antonio,Venturello, Paolo
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p. 9728 - 9741
(2007/10/03)
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- Sterically demanding cyclopentadienyl chemistry: Synthesis of iron and zirconium complexes of 1-phenyl-3-methyl-4,5,6,7-tetrahydroindenyl
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Reaction of phenyl magnesium bromide with the α,β-unsaturated ketone 3-methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one, followed by an aqueous work-up, generates the pro-chiral tetra-substituted cyclopentadiene, 1-phenyl-3-methyl-4,5,6,7-tetrahydroindene, Cp?H, a precursor to the η5-cyclopentadienyl ligand in (Cp?)2Fe and [(Cp?)Fe(CO)]2(μ-CO)2. Both complexes were generated as mixtures of rac-(RR and SS)- and meso-(RS)-isomers, and in either case pure meso-isomer was isolated by crystallisation and characterised by single crystal X-ray structure, both molecules having crystallographic Ci symmetry. Reduction with Na/Hg cleaves meso-(RS)-[(Cp?)Fe(CO)]2(μ-CO)2 and the resulting mixture of (R)- and (S)-[(Cp?)Fe(CO)2]- anions reacts with MeI to give racemic (Cp?)Fe(CO)2Me, which was characterised by the X-ray crystal structure. The Cp? ligand is more electron donating than (η-C5H5) as revealed by the reduction potential of the (Cp?)2Fe+/(Cp?) 2Fe couple, E°=-0.127 V (vs. Ag AgCl). Reaction of LiCp? with ZrCl4 yields the zirconocene dichloride [Zr(Cp?)2Cl2] as mixture of rac- and meso-isomers, from which pure rac-isomer is obtained as a mixture of RR and SS crystals by recrystallisation. The reaction of rac-[Zr(Cp?)2Cl2] with LiMe gives rac-[Zr(Cp?)2Me2]. The structures of RR-[Zr(Cp?)2Cl2] and rac-[Zr(Cp?)2Me2] have been determined by X-ray diffraction. The structural studies reveal the influence of the bulky substituted cyclopentadienyl ligand on the metal-Cp? distances and other metric parameters.
- Batsanov, Andrei S.,Bridgewater, Brian M.,Howard, Judith A.K.,Hughes, Andrew K.,Wilson, Claire
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p. 169 - 179
(2007/10/03)
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- Titanium(II) or zirconium(II) complexes and addition polymerization catalysts therefrom
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Novel titanium or zirconium complexes containing one and only one cyclic delocalized, anionic, ?-bonded group wherein the metal is in the +2 formal oxidation state and having a bridged ligand structure, also referred to as constrained geometry complexes; catalytic derivatives of such complexes; methods of preparation; and the use thereof as catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers.
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- Phosphane Alkylenes, 53. - Synthesis of α,β-Unsaturated Cycloalkanones from Bis - A Method for the Transformation of Acid Anhydrides into Carbocyclic and Heterocyclic Compounds
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Alkaline hydrolysis of bis 3 leads to 2-cycloalken-1-ones 6.Intramolecular Wittig reaction of an intermediately formed monoacyl ylide 4 and intramolecular aldol condensation of a diketone 5, resulting from hydrolysis of both ylide functions, are discussed as possible reaction mechanisms.The oxidation of 3 with H2O2 * Ph3PO yields 7- and 8-membered 2-cycloalkene-1,4-diones 12, presumely via mono ylides 11 carrying an aldehyde group in the ω-position.The reactions of 3 with aldehydes (molar ratio 1:1) lead to the formation of mono Wittig compounds 15 which can cyclize affording 5- and 6-membered 3-alkenyl-2-cycloalken-1-ones 16.Since the ylides 3 are easily available from acid anhydrides the reaction sequences represent versatile approaches for the transformation of acid anhydrides into 2-cycloalken-1-ones. Key Words: Phosphonium ylides / Wittig reactions, intramolecular / Aldol condensations, intramolecular / 2-Cycloalken-1-ones / 2-Cycloalken-1,4-diones
- Bestmann, Hans Juergen,Pichl, Rainer,Zimmermann, Reiner
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p. 725 - 732
(2007/10/02)
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- Nazarov cyclisation of dienone-esters and tetrahydropyrones using trimethylsilyltriflate
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Cyclopentenone esters have been synthesized via a Nazarov cyclisation of the corresponding α,α'-dienone esters or tetrahydro-γ-pyrone esters employing trimethylsilyltriflate at room temperature. The dienone esters were synthesised by a short two-step acylation-Knoevenagel sequence.
- Andrews,Regan
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p. 7731 - 7734
(2007/10/02)
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- PALLADIUM-CATALYZED DIASTEREOSELECTIVE SYNTHESES OF (E)-1-TRIMETHYLSILYL-2-ALKENES, (E)-1-TRIMETHYLSILYL-1-ALKEN-3-YNES, (1E,5E)-1-TRIMETHYLSILYL-1,5-ALKADIEN-3-YNES, (1E,3Z)- AND (1E,3E)-1-TRIMETHYLSILYL-1,3-ALKADIENES
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On the basis of our observation that (E)-1-bromo-1-alkenes undergo preferentially stereospecific Pd-catalyzed cross-couplings with a variety of organometallics, in the presence of the corresponding (Z)-stereoisomers, efficient and convenient diastereoselective procedures have been developed to prepare nearly stereoisomerically pure (E)-1-trimethylsilyl-2-alkenes (4), (E)-1-trimethylsilyl-1-alken-3-ynes (5), (1E,5E)-1-trimethylsilyl-1,5-alkadien-3-ynes (6), and (1E,3E)-1-trimethylsilyl-1,3-alkadienes (8) from stereoisomeric mixtures of alkenyl bromides.Compounds 5 have been stereoselectively converted into (1E,3Z)-1-trimethylsilyl-1,3-dienes (7) by selective hydrometallations, followed by hydrolysis.Some synthetic applications of compounds 5-8 have been also examined.
- Andreini, Bianca Patrizia,Carpita, Adriano,Rossi, Renzo,Scamuzzi, Barbara
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p. 5621 - 5640
(2007/10/02)
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- Three carbon annelation reagents: unsaturated alpha aminonitriles as homoenolate equivalents
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α-Aminonitriles and (R = Me) can react as either acyl anion or β-homoenolate equivalents on varying the reaction conditions. Both modes of reaction are potentially useful in three carbon annelations.
- Jacobson, Richard M.,Clader, John W.
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p. 1205 - 1208
(2007/10/02)
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- Three-Carbon Annelations. Regiocontrolled Reactivity of Trimethylsilyl- and Ethoxyethyl-Protected Cyanohydrins. Versatile Homoenolate and Acyl Anion Equivalents
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The trimethylsilyl- (2) and ethoxyethyl- (4) protected cyanohydrins of α,β-unsaturated aldehydes are utilized as three-carbon annelation reagents.Metalated reagent 2 displays exclusive α reactivity with aldehydes and ketones at -78 deg C.Metalated reagent 4 displays exclusive α reactivity at -78 deg C and exclusive γ reactivity at 0 deg C.Reagent 4 thus allows for complete regiocontrol in its addition to aldehydes and ketones which permits selective addition of either a homoenolate or an acyl anion equivalent.Metalation of the α product 11 at -78 deg C with subsequent warming to 0 deg C produces exclusively the γ product, confirming the reversible nature of the addition to the carbonyl.The derived α '-trimethylsiloxy enones 17 (R3=Me3Si), α '-hydroxy enones 17 (R3=H), α '-acetoxyenones 17 (R3=Ac), and γ-lactones 10 are useful cyclopentenone precursors.Treatment of 17 with p-TsOH in toluene at reflux produces cyclopentenones.The reaction proceeds via the postulated intermediacy of a pentadienyl cation 15 which undergoes in situ electrocyclic ring closure.
- Jacobson, Richard M.,Lahm, George P.,Clader, John W.
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p. 395 - 405
(2007/10/02)
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- Silanes in Organic Synthesis. 8. Preparation of Vinylsilanes from Ketones and Their Regiospecific Cyclopentenone Annulation
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A general method is described for the formation of vinylsilanes from ketones.Thus, conversion to the benzene- or p-toluenesulfonylhydrazone and sequential treatment with n-butyllithium and chlorotrimethylsilane in anhydrous tetramethylethylenediamine proceeds regiospecifically to afford the less substituted vinylsilane (in unsymmetrical cases).Friedel-Crafts acylation with acryloyl chlorides and aluminium chloride and subsequent Nazarov cyclization with Lewis acid catalysis results in cyclopentenone annulation.Numerous examples that reveal the scope of this processare described.Due to accompanying polymerization, annulation with acryloyl chloride itself is least efficient.This complication can, however, be averted through use of β-chloropropionyl chloride and dehydrochlorination with 1,5-diazabicycloundec-5-ene prior to ring closure.
- Paquette, Leo A.,Fristad, William E.,Dime, David S.,Bailey, Thomas R.
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p. 3017 - 3028
(2007/10/02)
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