Photochemical generation and 1H NMR detection of alkyl allene oxides in solution

2005 ◽  
Vol 83 (9) ◽  
pp. 1347-1351 ◽  
Author(s):  
Leah E Breen ◽  
Norman P Schepp ◽  
C-H Edmund Tan
Keyword(s):  
Nmr Spectroscopy ◽  
Significant Influence ◽  
Alkyl Group ◽  
Room Temperature ◽  
Nucleophilic Attack ◽  
Allene Oxide ◽  
Lifetime Measurements ◽  
H Nmr ◽  
Photochemical Generation ◽  
Allene Oxides

Irradiation of substituted 5-alkyl-4,5-epoxyvalerophenones leads to the formation of alkyl allene oxides that, in some cases, are sufficiently long-lived to be detected at room temperature by 1H NMR spectroscopy. Absolute lifetime measurements show that the size of the alkyl group has a significant influence on the reactivity of the allene oxide, with tert-butyl allene oxide having a lifetime of 24 h in CD3CN at room temperature that is considerably longer than the 1.5 h lifetime of the ethyl allene oxide. The allene oxides react rapidly with water to give α-hydroxyketones. The mechanism involves nucleophilic attack to the epoxide carbon to give an enol, which can also be detected as an intermediate by 1H NMR spectroscopy.Key words: allene oxides, mechanisms, absolute reactivity, kinetics, photochemistry.

Das dynamische Verhalten des 1-Methyl-1-benzothiepinium-Ringsystems/The Dynamic Behaviour of the 1-Methyl-1-benzothiepinium Ring System

1981 ◽  
Vol 36 (8) ◽  
pp. 974-977 ◽  
Author(s):  
Hans Hofmann ◽  
Franz Dickert
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
Dynamic Behaviour ◽  
Ring System ◽  
Membered Ring ◽  
Ring Inversion ◽  
Methyl Group ◽  
H Nmr ◽  
Pyramidal Inversion ◽  
Mutual Conversion

Abstract By 1H NMR spectroscopy the stereochemistry of the 1-methyl-1-benzothiepinium ring system was investigated both in thermodynamic and kinetic respects. It was shown that in solution a rapid mutual conversion of the boat shaped seven membered ring system with exo-respectively endo-S-methyl group occurs via a ring inversion and not by a pyramidal inversion at the sulfonium ion. At room temperature predominantly the conformation with the exo-S-methyl group is present.

Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

1994 ◽  
Vol 72 (7) ◽  
pp. 1675-1683 ◽  
Author(s):  
Jacques Poitras ◽  
André L. Beauchamp
Keyword(s):  
Infrared Spectroscopy ◽  
Nmr Spectroscopy ◽  
Crystal Structures ◽  
Infrared Spectra ◽  
Oxidative Coupling ◽  
Room Temperature ◽  
H Nmr ◽  
Counter Ion ◽  
Distorted Octahedral ◽  
Complex Salts

The reaction of NbCl5 and TaCl5 with 7-azaindole (Haza) at room temperature in benzene or dichloromethane yielded MCl5(Haza) addition compounds. Under more severe conditions, the same compound was obtained with TaCl5. For NbCl5, some reduction to Nb(IV) was observed and NbCl5(Haza), NbCl4(Haza)2, and the (H2aza)+ ion were identified in the reaction mixture by infrared spectroscopy. Oxidative coupling of two azaindole units via N7—C6 also took place during the reaction, since the 7-(azaindol-6-yl)azaindolium cation was found as counter-ion in the crystal structures of two complex salts. In the crystals of (H2aza-aza)[NbOCl4(Haza)]•0.5CH2Cl2([Formula: see text]a = 7.255 Å, b = 12.412 Å, c = 14.277 Å, α = 89.03°, β = 85.60°, γ = 76.66°, Z = 2, R = 0.062), the anion is the roughly octahedral [NbOCl4(azaindole)]− species containing a neutral N7-coordinated azaindole trans to the Nb=O bond. The [NbOCl5]2− salt ([Formula: see text]a = 7.527 Å, b = 10.168 Å, c = 10.467 Å, α = 66.41°, β = 84.07°, γ = 85.51°, Z = 1, R = 0.037) contains the distorted octahedral [NbOCl5]2− ion disordered over two orientations. The infrared spectra suggest monomeric octahedral structures for the MCl5(Haza) and NbCl4(Haza)2 complexes. 1H NMR spectroscopy shows that NbCl5(Haza) is not dissociated in CD2Cl2.

scholarly journals The photoisomerization of cis,trans-1,2-dideuterio-1,4-diphenyl-1,3-butadiene in solution. No bicycle-pedal

2019 ◽  
Vol 18 (9) ◽  
pp. 2174-2179
Author(s):  
Jack Saltiel ◽  
Christopher E. Redwood ◽  
Ratheesh Kumar V. K.
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
H Nmr

cis,trans-1,2-Dideuterio-1,4-diphenyl-1,3-butadiene (ct-DPBd2) was synthesized and its cis–trans photoisomerization in cyclohexane-d12 (C6D12) at room temperature was monitored by 1H NMR spectroscopy.

Primary and secondary 5-(alkyloxy)thianthrenium perchlorates. Characterization with 1H NMR spectroscopy, reactions with iodide and bromide ion, and thermal decomposition in solution

1998 ◽  
Vol 76 (6) ◽  
pp. 695-702 ◽  
Author(s):  
Wenyi Zhao ◽  
Henry J Shine
Keyword(s):  
Nmr Spectroscopy ◽  
Alkyl Group ◽  
Alkyl Halide ◽  
Cation Radical ◽  
Side Reaction ◽  
Alkyl Iodide ◽  
Order Kinetic ◽  
H Nmr ◽  
Bromide Ion ◽  
Stereogenic Center

A series of 5-(alkyloxy)thianthrenium perchlorates has been made in which the alkyl group is primary (1a-1p) and secondary (2a-2g). Preparations were carried out by reaction of the corresponding alkanol with thianthrene cation radical perchlorate in CH2Cl2 solution followed by precipitation of the perchlorate salt with dry ether. 1H NMR spectroscopy reveals that the presence of a stereogenic center in the alkyl group causes inequivalence in the ordinarily paired protons (e.g., H-4, H-6) of the thianthrenium ring. Reaction of iodide and bromide ion with primary alkyl-group compounds (e.g., methyl, ethyl, propyl, butyl) gave the alkyl halide in very good yield and by a second-order kinetic displacement. The second product was thianthrene 5-oxide (ThO). Rate constants for some of these reactions are reported. Reaction of secondary alkyl group compounds (e.g., 2-propyl, 2-pentyl, 2-hexyl, and 3-hexyl) with iodide ion gave good yields of alkyl iodide but also increasing evidence for a side reaction at the sulfonium sulfur, leading to I2, thianthrene, and secondary alkanol. Decomposition of some compounds at 100°C in solution (acetonitrile or 1,2-dichloroethane) was studied and gave alkene(s) and ThO.Key words: thianthrene cation radical, 5-(alkyloxy)thianthrenium perchlorates.

scholarly journals Stereochemistry of Two Hydroxybiflavanonols from Garcinia cola Nuts

1987 ◽  
Vol 42 (7-8) ◽  
pp. 855-857 ◽  
Author(s):  
Johann Sonnenbichler ◽  
Ifeanyi Madubunyi ◽  
Hugo Scheer
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Room Temperature ◽  
H Nmr ◽  
The Absolute

The absolute configuration of two hydroxybiflavanonols from Garcinia cola nuts have been determined by CD and 500 MHz 1H NMR spectroscopy. Additionally the occurrence of atrop-isomers at room temperature as the consequence of rotational hindrance in the molecules could be demonstrated.

Carbon versus oxygen nucleophilic selectivity in the reaction of the aryloxide ions, 2,6- and 3,5-di-tert-butylphenoxide, with the 2-[(nitro)\dn6 xaryl]-4,6-dinitrobenzotriazole 1-oxide series of super-electrophiles. Stereoelectronic factors on C-7 Meisenheimer complex formation versus C-1' SNAr displacement

1998 ◽  
Vol 76 (6) ◽  
pp. 662-671 ◽  
Author(s):  
Julian M Dust ◽  
Richard A Manderville
Keyword(s):  
Nmr Spectroscopy ◽  
Nucleophilic Aromatic Substitution ◽  
Nucleophilic Attack ◽  
Aromatic Substitution ◽  
Factors Affecting ◽  
H Nmr ◽  
Sterically Demanding ◽  
Biphenyl Derivative ◽  
First Time ◽  
Electrophilic Site

The 2-[(nitro)xaryl]-4,6-dinitrobenzotriazole 1-oxides (1, Pi-DNBT (x = 3); 2, DNP-DNBT (x = 2); 3, NP-DNBT (x = 1)) are electron-deficient nitro-substituted heteroaromatic substrates that possess two sites for nucleophilic attachment: C-7 and C-1'. Generally, attack at the super-electrophilic C-7 site yields spectroscopically observable anionic sigma -bonded adducts, whereas attack at C-1' leads to displacement products in an overall process of nucleophilic aromatic substitution (SNAr). To gain an understanding of the factors affecting C-1' versus C-7 attack by potentially ambident aryloxide (C- and O-)nucleophiles, we have monitored the reactions of 1-3 with 2,6-di-tert-butylphenoxide (2,6-ArO-) and 3,5-di-tert-butylphenoxide (3,5-ArO-) using 400 MHz 1H NMR spectroscopy (deuterated dimethyl sulfoxide solvent at ambient temperature). The results indicate that 2,6-ArO- acts only as a C-nucleophile with O-attack precluded, presumably by the sterically demanding tert-butyl groups flanking the O-nucleophilic centre. Although 2,6-ArO- reacts preferentially at C-7 of 1-3, the biphenyl derivative that arises from C-1' attack is also observed with 1, the first time that C-nucleophilic attack has been seen at this electrophilic site. In contrast, 3,5-ArO- acts only as an O-nucleophile, also as a consequence of the steric hindrance to the C-4 position; this aryloxide reacts entirely at C-1' of Pi-DNBT but also exclusively at C-7 of 3. However, with DNP-DNBT, 2, both the C-7 O-adduct and C-1' displacement products are noted; attack at C-1' is dominant. The selectivity (C-7 versus C-1') found in these reactions is discussed with emphasis given to stereoelectronic factors that may stabilize the putative C-1' O-adducts.Key words: aryloxides, super-electrophiles, Meisenheimer complexes, 2-[(nitro)xaryl]-4,6-dinitrobenzotriazole 1-oxides.

Application of NMR Spectroscopy to the Study of Piperidine Derivatives. Part III: Molecular Dynamics Study of N-Benzyl-4-[N-Benzyloxyacetyl)-(2-Fluorophenyl)]Amino-3-Methyl Piperidine

1993 ◽  
Vol 47 (3) ◽  
pp. 357-359 ◽  
Author(s):  
A. L. Cholli ◽  
M. L. Lau
Keyword(s):  
Molecular Dynamics ◽  
Nmr Spectroscopy ◽  
High Resolution ◽  
Detailed Analysis ◽  
Room Temperature ◽  
Variable Temperature ◽  
Proton Nmr ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Nmr Data

High-resolution 1H NMR has been used to study the molecular dynamics of the piperidine derivative. Detailed analysis of variable temperature NMR data allowed the identification of the origin of two sets of methyl resonance peaks with unequal intensities in the room-temperature proton NMR spectrum of the compound.

The Preparation of Some Mono-and Bis(thiolate)-2-butyne Complexes of Tungsten(II) of the Types [WI(SR)(CO)(dppm )(η2-MeC2Me)] {dppm = Ph2P(CH2)PPh2; R = Et, But, Ph or CH2Ph} and [W (SR)2(CO)(dppm)(η2-MeC2Me)]

1994 ◽  
Vol 49 (11) ◽  
pp. 1544-1548 ◽  
Author(s):  
Paul K. Baker ◽  
Kevin R. Flower
Keyword(s):  
Nmr Spectroscopy ◽  
Elemental Analysis ◽  
Good Yield ◽  
Nmr Spectra ◽  
Room Temperature ◽  
H Nmr ◽  
Thiolate Complexes ◽  
C Nmr

Equimolar quantities of [WI(CO)(NCMe)(dppm)(η2-MeC2Me)][BF4] {dppm = Ph2P(CH2)PPh2) and NaSR (R = Et. But ,Ph or CH2Ph) react in CH2Cl2 at room temperature to give the neutral thiolate complexes [WI(SR)(CO)(dppm)(η2-MeC2Me)] (1 → 4) in good yield. The complex [WI(CO)(NCMe)(dppm)(η2-MeC2Me)][BF4] also reacts with two equiv­alents of NaSR (R = Et. But, Ph or CH2Ph) in CH2Cl2 at room temperature to afford the bis(thiolate) complexes [W(SR)2(CO)(dppm)(η2-MeC2Me)] (5 → 8), in good yield. Com­plexes 1→8 have been characterized by elemental analysis (C, H and N), IR and 1H NMR spectroscopy. 13C NMR spectra of selected complexes indicate that the 2-butyne ligand is donating four electrons to the metal in both [WI(SR)(CO)(dppm)(η2-MeC2Me)] and [W(SR)2(CO)(dppm)(η2-MeC2Me)] type complexes.

Derivatives of cis-NPCl2(NSOCl)2 and (NPCl2)2NSOCl, Part X [1] Aminolysis of cis-NPCl2(NSOF)2 and (NPCl2)2NSOF

1978 ◽  
Vol 33 (9) ◽  
pp. 964-967 ◽  
Author(s):  
H. H. Baalmann ◽  
J. C. van de Grampel
Keyword(s):  
Data Structure ◽  
Nmr Spectroscopy ◽  
Spectral Data ◽  
Room Temperature ◽  
Nucleophilic Attack ◽  
Ring Systems ◽  
Cyclic Amines ◽  
Amino Derivatives ◽  
Derivatives Of

The aminolysis of the ring systems cis-NPCl2(NSOF)2 and (NPCl2) 2NSOF by cyclic amines in acetonitrile at room temperature shows the S-F bond to be stable towards a nucleophilic attack. The amino derivatives are characterized by their spectral data. Structure assignments are based on 31P NMR spectroscopy.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

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