Generation of four five-membered rings in a one pot process. Studies directed toward the synthesis of dicyclopenta[a,d]pentalene via the tandem Pauson-Khand reaction

Ornum, Scott G. Van; Cook, James M.

doi:10.1016/0040-4039(96)01634-6

Cited by 33 publications

(13 citation statements)

References 14 publications

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“…Attempts to generate compounds of 18-20 have not been successful [45][46][47]. According to the %TREs, compound 19 is more stable than 20, which is in agreement with the B3LYP/6-31G * level calculation results [46].…”

Section: B Molecular Ionssupporting

confidence: 78%

“…17 is antiaromatic and to date has been observed in mass spectrometry experiments [43], but 17 2− is a stable nonplanar aromatic species which has been prepared by Meijere and co-workers [44]. Attempts to generate compounds of 18-20 have not been successful [45][46][47]. According to the %TREs, compound 19 is more stable than 20, which is in agreement with the B3LYP/6-31G * level calculation results [46].…”

Section: B Molecular Ionssupporting

confidence: 71%

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Aromaticity of Heterofullerenes C18BxNy(x+y= 2) and Their Molecular Ions

Chen

Kerim

2008

Chinese Journal of Chemical Physics

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The aromaticity of all possible substituted fullerene isomers of C 18 N 2 , C 18 B 2 , C 18 BN, and their molecular ions which originate from the C 20 (I h ) cage were studied by the topological resonance energy (TRE) and the percentage topological resonance energy methods. The relationship between the aromaticity of C 18 BxNy isomers and the sites where the heteroatoms dope at the C 20 (I h ) cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C 18 N 2 , C 18 B 2 , and C 18 BN. Heterofullerenes are more aromatic than C 20 . The stability order in the neutral states is C 18 N 2 >C 18 BN>C 18 B 2 >C 20 . The stability order in closed-shell is C 18 B 2 8− >C 20 6− >C 18 BN 6− >C 18 N 2 4− . This predicts theoretically that their polyvalent anions have high aromaticity.

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Section: B Molecular Ionssupporting

confidence: 78%

Section: B Molecular Ionssupporting

confidence: 71%

Aromaticity of Heterofullerenes C18BxNy(x+y= 2) and Their Molecular Ions

Chen

Kerim

2008

Chinese Journal of Chemical Physics

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“…Reagents were purchased from commercial sources, were degassed and stored in the dry-box when directly used in combination with organometallic complexes, and otherwise were used without further purification. 2-i-Propoxystyrene, 36 diethyldiallylmalonate (DEDAM), 37 diallylmalonic acid (DAM), 38 3,3-diallylpentane-2,4-dione (DAP), 39 and monomer 14 34a were synthesized according to literature procedures. Grubbs' catalyst 1 was purchased from Aldrich, degassed and stored in the dry-box.…”

Section: Methodsmentioning

confidence: 99%

Olefin metathesis catalysts bearing a pH-responsive NHC ligand: a feasible approach to catalyst separation from RCM products

et al. 2008

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Two novel ruthenium-based olefin metathesis catalysts, H(2)ITap(PCy(3))Cl(2)Ru[double bond, length as m-dash]CH-Ph and H(2)ITapCl(2)Ru[double bond, length as m-dash]CH-(C(6)H(4)-O-iPr) (H(2)ITap = 1,3-bis(2',6'-dimethyl-4'-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene), were synthesized bearing a pH-responsive NHC ligand with two aromatic NMe(2) groups. The crystal structures of complexes and were determined via X-ray crystallography. Both catalysts perform ring opening metathesis polymerization (ROMP) of cyclooctene (COE) at faster rates than their commercially available counterparts H(2)IMes(PCy(3))Cl(2)Ru[double bond, length as m-dash]CH-Ph and H(2)IMesCl(2)Ru[double bond, length as m-dash]CH-(C(6)H(4)-O-iPr) (H(2)IMes = 1,3-bis(2',4',6'-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) and perform at similar rates during ring closing metathesis (RCM) of diethyldiallylmalonate (DEDAM). Upon addition of 2 equiv. of HCl, catalyst is converted into a mixture of several mono and diprotonated Ru-carbene species 12' which are soluble in methanol but degrade within a few hours at room temperature. Catalyst can be protonated with 2 equiv. of HCl and the resulting complex is moderately water-soluble. The complex is stable in aqueous solution in air for >4 h, but over prolonged periods of time shows degradation in acidic media due to hydrolysis of the NHC-Ru bond. Catalysts and perform RCM of diallylmalonic acid in acidic protic media with only moderate activity at 50 degrees C and do not produce polymer in the ROMP of cationic 7-oxanorbornene derivative under the same conditions. Catalyst was used for Ru-seperation studies when RCM of DEDAM or 3,3-diallypentadione (DAP) was conducted in low-polar organic solution and the Ru-species was subsequently precipitated by addition of strong acid. The Ru-species were removed by (1) filtration and (2) filtration and subsequent extraction with water. The residual Ru-levels could be reduced to as far as 11 ppm (method 2) and 24 ppm (method 1) without the use of chromatography or other scavenging methods.

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“…Other chemicals and reagents were purchased from commercial sources, and they were degassed and stored in the dry-box when directly used in combination with organometallic complexes, and otherwise were used without further purification. H 2 ITap∙HCl, complex 8 , as well as DEDAM and DAMA were synthesized according to literature procedures [ 61 , 71 ].…”

Section: Methodsmentioning

confidence: 99%

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

Balof¹,

Nix²,

Olliff³

et al. 2015

Beilstein J. Org. Chem.

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SummaryThree new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes.

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Generation of four five-membered rings in a one pot process. Studies directed toward the synthesis of dicyclopenta[a,d]pentalene via the tandem Pauson-Khand reaction

Cited by 33 publications

References 14 publications

Aromaticity of Heterofullerenes C18BxNy(x+y= 2) and Their Molecular Ions

Aromaticity of Heterofullerenes C18BxNy(x+y= 2) and Their Molecular Ions

Olefin metathesis catalysts bearing a pH-responsive NHC ligand: a feasible approach to catalyst separation from RCM products

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

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