New pseudohalide ligands in Ru-catalyzed olefin metathesis — A robust, air-activated iminopyrrolato catalyst

2005 ◽  
Vol 83 (6-7) ◽  
pp. 748-754 ◽  
Author(s):  
Samantha D Drouin ◽  
Heather M Foucault ◽  
Glenn PA Yap ◽  
Deryn E Fogg
Keyword(s):  
Key Words ◽  
Olefin Metathesis ◽  
High Reactivity ◽  
Ring Closing Metathesis ◽  
Grubbs Catalyst ◽  
X Ray ◽  
X Ray Crystallography

Reaction of the Grubbs catalyst RuCl2(PCy3)2(CHPh) (1) with lithium 2-[(2,6-diisopropylphenyl)imino]pyrrolide·Et2O (LiNN′·Et2O) gives alkylidene complex 5, containing a chelating, σ-bound iminopyrrolato unit. The structure of 5 is confirmed by X-ray crystallography. Treatment of 5 with pyridine generates RuCl(NN′)(py)2(CHPh) (6) via displacement of PCy3. Complex 5 effects ring-closing metathesis in air, displaying high reactivity relative to 6.Key words: ruthenium, alkylidene, metathesis, pyrrolimine, iminopyrrolato.

Synthesis and characterization of the binuclear diamido titanium chalcogenides [(Ar)NCH2CH2CH2N(Ar)]2Ti(µ-E)2 (E = Se, Te)

2002 ◽  
Vol 80 (11) ◽  
pp. 1524-1529 ◽  
Author(s):  
Tianle Zhang ◽  
Warren E Piers ◽  
Masood Parvez
Keyword(s):  
Solid State ◽  
Key Words ◽  
Synthesis And Characterization ◽  
Catalyst Precursor ◽  
Tellurium Atom ◽  
Titanium Complex ◽  
X Ray ◽  
X Ray Crystallography ◽  
Atom Source

Reaction of McConville's chelating amido titanium complex [(Ar)NCH2CH2CH2N(Ar)]Ti(CH3)2 (Ar = 2,6-i-Pr2C6H3) with either elemental Se or the tellurium atom source Te=PBu3 resulted in the formation of bis-µ-chalcogenido dimers [(Ar)NCH2CH2CH2N(Ar)]2Ti(µ-E)2 (E = Se, 2; Te, 3) with concommitant loss of EMe2. The dimers 2 and 3 were characterized spectroscopically and via X-ray crystallography. The two compounds are isostructural in the solid state. The tellurido dimer 3 may also be synthesized by reduction of the diamido dichloride [(Ar)NCH2CH2CH2N(Ar)]2TiCl2 with Na–Hg amalgam followed by treatment with Te=PBu3. This dimer is unreactive toward further Te=PBu3 or stannanes such as HSnBu3. Unlike decamethyltitanocene derivatives, the diamido complex is not an effective catalyst precursor for the heterohydrodecoupling of Te=PBu3 and HSnBu3.Key words: diamido titanium complexes, selenides, tellurides.

A facile new procedure for the deprotection of allyl ethers under mild conditions

2000 ◽  
Vol 78 (6) ◽  
pp. 838-845 ◽  
Author(s):  
Yun-Jin Hu ◽  
Romyr Dominique ◽  
Sanjoy Kumar Das ◽  
René Roy
Keyword(s):  
Key Words ◽  
Catalytic System ◽  
Olefin Metathesis ◽  
Allyl Ether ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Allyl Ethers ◽  
Mild Conditions ◽  
Cross Metathesis ◽  
Allylic Ethers

A novel isomerization of O-allyl glycosides into prop-1-enyl glycosides was observed instead of cross-metathesis during an olefin metathesis reaction using Grubbs' ruthenium benzylidene catalyst (Cy3P)2RuCl2=CHPh (1), N-allyltritylamine, and N,N-diisopropylethylamine as necessary auxiliary reagents. In the search for a better catalytic system, it has been found that dichlorotris(triphenylphosphine)ruthenium(II), [(C6H5)3P]3RuCl2, (2) was much more efficient for the isomerization of allylic ethers. The labile prop-1-enyl group was easily hydrolyzed using HgCl2-HgO and the hemiacetals (25-32) were isolated in excellent yields (ca. 90%).Key words: allyl ether, carbohydrate, Grubbs' catalyst, isomerization, metathesis, deprotection.

Six pyrimidonium salts: determination of their crystal structures and studies of their prototropic behaviour in solution

1984 ◽  
Vol 62 (6) ◽  
pp. 1194-1202 ◽  
Author(s):  
Thomas W. S. Lee ◽  
Steven J. Rettig ◽  
Ross Stewart ◽  
James Trotter
Keyword(s):  
Hydrogen Exchange ◽  
Molecular Geometry ◽  
High Reactivity ◽  
Methyl Groups ◽  
Contributing Factors ◽  
X Ray ◽  
X Ray Crystallography ◽  
Reactive Compound ◽  
Chloride Salts

Six methyl-substituted 2-pyrimidonium chloride salts have been prepared and the rates of hydrogen exchange of their reactive methyl groups (at the 4- and 6-positions) have been determined in DCl/D2O solution. Adjacent methyl groups, whether on nitrogen or carbon, activate the exchanging centres, whereas more distant methyl groups have a deactivating effect. The molecular geometry of the salts has been determined by X-ray crystallography with the view to determining whether the presence of strain in the pyrimidonium ring can account for the activating effect of adjacent methyl. The most reactive compound, the 1,5,6-trimethylpyrimidonium chloride, has a geometry that is consistent with high reactivity, viz. a non-planar ring and short H … H intermethyl distance. However, the 1,4,5,6-tetramethyl compound, which also is non-planar and has an extremely short 5-6 intermethyl distance (1.99 Å), is not highly reactive; that is, the heightened strain is unable to overcome the deactivating inductive effect of the additional methyl group. We conclude that deviations from ring planarity and short intermethyl distances are insufficient to account for the activation produced by adjacent methyl though they appear to be contributing factors to this effect.

Alkoxide-functionalized cyclopentadienyl complexes of yttrium containing a two-carbon tether

2002 ◽  
Vol 80 (10) ◽  
pp. 1285-1292 ◽  
Author(s):  
Roland AL Gendron ◽  
David J Berg ◽  
Tosha Barclay
Keyword(s):  
Solid State ◽  
Key Words ◽  
Intramolecular Cyclization ◽  
Thermal Reaction ◽  
Chloride Complex ◽  
State Structure ◽  
Reduced Pressure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cyclopentadienyl Complexes

The ligand C5H4(CH2CH2CArF2OH) (3) (ArF = 3,5-C6H3(CF3)2) was prepared in two steps, from the iodo ester ICH2CH2CO2Me by way of the cyclopentadienyl ester C5H5CH2CH2CO2Me (2), in 55% overall yield. Thermal reaction of 3 with {Y[N(SiMe3)2]2(THF)2(µ-Cl)}2 afforded the neutral chloride complex {η5:η1-C5H4[CH2CH2C(O)(3,5-C6H3(CF3)2)2]}YCl{THF}n (5a: n = 2, 5b: n = 1). Metathesis reactions of 5 with 1 equiv of NaN(SiMe3)2, LiO-2,6-t-Bu2C6H3, and LiCH(SiMe3)2 afforded {η5:η1-C5H4[CH2CH2C(O)(3,5-C6H3(CF3)2)2]}Y{N(SiMe3)2}{THF}n (6), {η5:η1-C5H4[CH2CH2C(O)(3,5-C6H3(CF3)2)2]}Y{O-2,6-t-Bu2C6H3}{THF}n (7), and {η5:η1-C5H4[CH2CH2C(O)(3,5-C6H3(CF3)2)2]}Y{CH(SiMe3)2}{THF}n (8), respectively, (a: n = 2, b: n = 1). Exposure of the bis(THF) solvates to reduced pressure resulted in desolvation to the mono(THF) adducts for 5–8. The solid state structure of 6b was established by X-ray crystallography. In addition, formation of a spirocyclic ether (C4H6CH2CH2C(O)(3,5-C6H3(CF3)2)2 4), obtained by the intramolecular cyclization of ligand 3, was confirmed by X-ray crystallography. Key words: yttrium, organometallic, cyclopentadienyl, X-ray, alkoxide, chelate, alkyl, hybrid ligand, NMR, cyclization.

scholarly journals Synthesis of 2,24-Diene-12,13,15,16,34,35,37,38-octaphenyl[4.4]triphenylparacyclophane

Synthesis ◽  
2021 ◽  
Author(s):  
Duy H. Hua ◽  
Bernard Wiredu ◽  
Mahendra Thapa ◽  
Sheen Y. Hua ◽  
John Desper
Keyword(s):  
Olefin Metathesis ◽  
Knoevenagel Condensation ◽  
Coupling Reaction ◽  
Diels Alder ◽  
Synthetic Methodology ◽  
X Ray ◽  
X Ray Crystallography ◽  
Vinyl Group ◽  
Synthetic Intermediate

AbstractA new octaphenyl[4.4]triphenylparacyclophanediene was readily synthesized in six steps from p-xylene via the installment of bromine atoms, replacement with a vinyl group, carbonylative coupling, intermolecular followed by intramolecular double Grubbs olefin metathesis, Knoevenagel condensation, and Diels–Alder cycloaddition. The belt-shaped structure and trans-stereochemistry of the alkene moieties of the octaphenyl[4.4]triphenylparacyclophane and a synthetic intermediate, 2,21-dioxo-11,30-diene[3.4.3.4]paracyclophane, were determined by X-ray crystallography. The synthetic methodology leading to octaphenyl[4.4]triphenylparacyclophane is applicable for the synthesis of substituted triphenylparacyclophanes and possibly their corresponding bis-hexabenzocoronenylparacyclophanes via a Scholl–Mullen oxidative aryl-aryl coupling reaction.

scholarly journals Ortho-Phenylene-Based Macrocyclic Hydrocarbons Assembled Using Olefin Metathesis

2020 ◽  
Author(s):  
Viraj kirinda ◽  
Briana Schrage ◽  
Christopher Ziegler ◽  
Scott Hartley
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Olefin Metathesis ◽  
Secondary Structures ◽  
Higher Order ◽  
Order Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Simple Strategy

While many foldamer systems reliably fold into well-defined secondary structures, higher order structure remains a challenge. A simple strategy for the organization of folded subunits in space is to link them together within a macrocycle. Previous work has shown that o-phenylenes can be co-assembled with rod-shaped linkers into twisted macrocycles, showing an interesting synergy between folding and thermodynamically controlled macrocyclization. In these systems the foldamer units were largely decoupled from each other both conformationally and electronically. Here, we show that hydrocarbon macrocycles, with very short ethenylene linkers, can be assembled from o-phenylenes using olefin metathesis. Characterization by NMR spectroscopy, X-ray crystallography, and ab initio calculations shows that the products are approximately triangular [3+3] macrocycles with helical o-phenylene corners in a heterochiral configuration. Their photophysics are dominated by the 4,4′-diphenylstilbene moieties, the longest conjugated segments, with further conjugation broken by the twisting of the o-phenylenes.

Synthesis, characterization, and reactivity of the first hafnium alkyl complex stabilized by amidate ligands

2005 ◽  
Vol 83 (6-7) ◽  
pp. 1037-1042 ◽  
Author(s):  
Robert K Thomson ◽  
Brian O Patrick ◽  
Laurel L Schafer
Keyword(s):  
Coordination Chemistry ◽  
Solid State ◽  
Key Words ◽  
Low Temperatures ◽  
Variable Temperature ◽  
X Ray ◽  
X Ray Crystallography ◽  
Exchange Processes ◽  
Hydrolysis Of

A photo and thermally stable bis(amidate)–dibenzyl complex of Hf ([DMP(NO)Ph]2Hf(CH2Ph)2(THF) (2a) was formed as a monosolvated THF adduct in near quantitative yield from Hf(CH2Ph)4 and N-2,6-dimethylphenyl(phenyl)amide (1). Isomerization between the THF-bound product and the THF-free product can be observed visually by the conversion from a red-orange product at low temperatures to a pale yellow product at high temperatures. Solid-state crystallographic characterization of the orange product confirmed its constitution as a monosolvated species. Kinetic parameters for the exchange of the THF moiety were determined from variable-temperature NMR experiments. The product of the hydrolysis of the Hf dibenzyl species by water was characterized by X-ray crystallography, and was found to be a rare tetrametallic Hf oxo cluster species (3).Key words: hafnium, protonolysis, amidate, coordination chemistry, organometallic chemistry, exchange processes.

scholarly journals Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

2019 ◽  
Vol 15 ◽  
pp. 769-779 ◽  
Author(s):  
Kirill B Polyanskii ◽  
Kseniia A Alekseeva ◽  
Pavel V Raspertov ◽  
Pavel A Kumandin ◽  
Eugeniya V Nikitina ◽  
...  
Keyword(s):  
Ring Opening ◽  
The Novel ◽  
Ring Closing Metathesis ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cross Metathesis ◽  
Grubbs Catalysts ◽  
Coordinate Bond ◽  
Metathesis Catalysts ◽  
Hofmann Cleavage

A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzylamines allowed us to obtain new Hoveyda–Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10−2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).

Stereoelectronic effects in sulfonyl compounds: axial orientation of an N-methyl group in a six-membered sultam

1998 ◽  
Vol 76 (2) ◽  
pp. 164-170 ◽  
Author(s):  
James Frederick King ◽  
Gay Yuyitung ◽  
Manjinder Singh Gill ◽  
Jeffrey Charles Stewart ◽  
Nicholas Charles Payne
Keyword(s):  
Single Crystal ◽  
Key Words ◽  
Axial Orientation ◽  
Anomeric Effect ◽  
Trans Form ◽  
Methyl Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stereoelectronic Effects ◽  
Negative Hyperconjugation

The trans form of octahydro-1-methyl-1H-2,1-benzothiazine 2,2-dioxide, in which a six-membered sultam unit is trans-fused to cyclohexane, has been synthesized. The single-crystal X-ray structure shows the molecule to have the N-methyl group in the axial orientation. The generalized anomeric effect believed to be responsible for the axial preference is estimated at =>2 kcal mol-1.Key words: generalized anomeric effect, negative hyperconjugation, sulfonamides, sultams, X-ray crystallography.

scholarly journals Ortho-Phenylene-Based Macrocyclic Hydrocarbons Assembled Using Olefin Metathesis

2020 ◽  
Author(s):  
Viraj kirinda ◽  
Briana Schrage ◽  
Christopher Ziegler ◽  
Scott Hartley
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Olefin Metathesis ◽  
Secondary Structures ◽  
Higher Order ◽  
Order Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Simple Strategy

While many foldamer systems reliably fold into well-defined secondary structures, higher order structure remains a challenge. A simple strategy for the organization of folded subunits in space is to link them together within a macrocycle. Previous work has shown that o-phenylenes can be co-assembled with rod-shaped linkers into twisted macrocycles, showing an interesting synergy between folding and thermodynamically controlled macrocyclization. In these systems the foldamer units were largely decoupled from each other both conformationally and electronically. Here, we show that hydrocarbon macrocycles, with very short ethenylene linkers, can be assembled from o-phenylenes using olefin metathesis. Characterization by NMR spectroscopy, X-ray crystallography, and ab initio calculations shows that the products are approximately triangular [3+3] macrocycles with helical o-phenylene corners in a heterochiral configuration. Their photophysics are dominated by the 4,4′-diphenylstilbene moieties, the longest conjugated segments, with further conjugation broken by the twisting of the o-phenylenes.

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