Chemoselective intramolecular annulation of 3-alkylindolines into dihydro or tetrahydrofuro[2,3-b]indoles

1997 ◽  
Vol 75 (7) ◽  
pp. 959-964 ◽  
Author(s):  
Oscar R. Suárez-Castillo ◽  
Manuel García-Velgara ◽  
Martha S. Morales-Ríos ◽  
Pedro Joseph-Nathan
Keyword(s):  
Alkyl Group ◽  
Grignard Reagent ◽  
Steric Effect ◽  
Aprotic Solvent ◽  
Protic Solvent ◽  
Ring Transformation

3-Alkyl-2-hydroxyindolines, conveniently prepared from 2-hydroxyindolenines and a Grignard reagent, cyclize in the aprotic solvent tetrahydrofuran to afford tetrahydro-3-cyano-2-oxofuro[2,3-b]indoles, while in the protic solvent methanol the chemoselectivity changed to give dihydro-2-amino-3-carbomethoxyfuro[2,3-b]indoles. The steric effect of the alkyl group on the reactivity of 3-alkyl-2-hydroxyindolines is discussed for both processes. The ring transformation of tetrahydro-3-cyano-2-oxofuro[2,3-b]indoles into dihydro-2-amino-3-carbomethoxyfuro[2,3-b]indoles via γ-lactone imines is also discussed. Keywords: furo[2,3-b]indoles, α-cyano-γ-lactones, chemoselectivity, ring transformation, β-enamino esters.

The Influence of the 2-Alkoxy Group and of C-5 Substituents on the Direction of Reductive Cleavage of 2-Alkoxytetrahydrofurans by AlH2Cl in Ether Solution

1972 ◽  
Vol 50 (10) ◽  
pp. 1502-1512 ◽  
Author(s):  
P. C. Loewen ◽  
Miss L. P. Makhubu ◽  
R. K. Brown
Keyword(s):  
Transition State ◽  
Alkyl Group ◽  
Steric Effect ◽  
Bond Cleavage ◽  
Alkoxy Group ◽  
Ring Cleavage ◽  
Relative Ease ◽  
Ether Solution ◽  
A Minor ◽  
Minor Extent

The AlH2Cl hydrogenolysis of ether solutions of 2-alkoxytetrahydrofurans in which the alkoxy group is either CH3O, C2H5O, i-C3H7O, or t-C4H9O, gives only those products resulting from ring C—O bond cleavage. However, substituents at C-5 of 2-methoxytetrahydrofuran exert a strong effect on the ratio of ring to exo C—O bond cleavage. Thus, alkyl (electron donor) groups at C-5 promote an increase in the amount of exo cleavage, the proportion increasing from 62.5 to 100% as the C-5 alkyl group is changed from CH3 to t-C4H9. In contrast, electron withdrawing substituents, CH3OCH2— and C6H5, at C-5 favor ring cleavage to the extent of 93 and 84% respectively.The results are interpreted in terms of the influence that these substituents exert through their electronic properties on the relative ease of attainment of the transition state leading to either ring C—O or exo C—O bond cleavage. However, evidence is provided to show that the bulk steric effect of these substituents also controls, though to a minor extent, the proportion of ring to exo cleavage.

Réactions dans le sulfolane. VI. Etude de solutions des acides perchlonque, fluorosulfurique, pyrosulfurique et hexachloroantimonique

1970 ◽  
Vol 48 (15) ◽  
pp. 2353-2359 ◽  
Author(s):  
R. L. Benoit ◽  
C. Buisson ◽  
G. Choux
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Aprotic Solvent ◽  
Strong Acid ◽  
Acid Strength ◽  
Protic Solvent ◽  
Dilute Solution ◽  
Conductivity Data ◽  
Dipolar Aprotic Solvent ◽  
Nuclear Magnetic

Nuclear magnetic resonance and certain conductivity data are reported for solutions of perchloric and fluorosulfuric acids in sulfolane. Additional measurements were made on solutions of disulfuric and hexachloroantimony (V) acids. HSbCl6 is a strong acid in this weakly basic dipolar aprotic solvent. HClO4, HSO3F, and H2S2O7 are incompletely dissociated with K = 10−2.7, 10−3.3, and ~ 10−5, respectively. The acid strength in dilute solution in sulfolane follows the order HClO4 > HSO3F > H2S2O7, which differs from that known in H2SO4 which is a strongly associated polar protic solvent.

Investigation of Solvent-Dependent Catalytic Behavior of a Hydrophobic Guest Artificial Glutathione Peroxidase

2014 ◽  
Vol 940 ◽  
pp. 20-23
Author(s):  
Yan Zhen Yin ◽  
Shu Fei Jiao ◽  
Xiong Gan ◽  
Zhong Feng Shi ◽  
Xiao Xi Hu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Glutathione Peroxidase ◽  
Aprotic Solvent ◽  
Protic Solvent ◽  
Catalytic Behavior ◽  
Polar Aprotic Solvent ◽  
Catalytic Rate

The investigation of the catalytic behavior of a hydrophobic guest artificial glutathione peroxidase (GPx) (ADA-Te-ADA) was carried out employing H2O2 and 3-carboxyl-4-nitrobenzenethiolas (TNB) as substrates. The relation between the catalytic rate of ADA-Te-ADA and the property of solvent used in the determination of catalytic activity was revealed. Typically, the co-solvents including ethanol, DMSO, DMF and CH3CN were employed in the determination of catalytic rates. It indicated that ADA-Te-ADA exhibited the typical solvent-dependent catalytic behavior. Especially, the higher catalytic rate was observed when polar protic solvent (ethanol) was used compared with other co-solvents. It suggested that polar protic solvent was the appropriate co-solvent for the assay of catalytic activity of hydrophobic artificial GPx. Additionally, the strong polarity of polar aprotic solvent plays an important role in the enhancement of GPx catalytic activity. This study bodes well for the understanding of the catalytic behavior of hydrophobic guest artificial GPx.

scholarly journals Synthesis, characterization and crystal structure of [Cu2(LH)2]•(ClO4)2. Influence of the weak Cu•••O(perchlorate) interaction on the structure of Cu2N2O2 metallocycle

2014 ◽  
Vol 79 (5) ◽  
pp. 545-556
Author(s):  
Marija Mirkovic ◽  
Nadezda Nikolic ◽  
Dusan Mijin ◽  
Milka Avramov-Ivic ◽  
Agnes Kapor ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cyclic Voltammetry ◽  
Schiff Base ◽  
Ir Spectroscopy ◽  
Metal Complex ◽  
Aprotic Solvent ◽  
Metal Salt ◽  
Protic Solvent ◽  
X Ray Diffraction ◽  
X Ray

The diimine-dioxime ligand, 4,9-diaza-3,10-diethyl-3,9-dodecadiene-2,11-dione bisoxime (LH2), containing a N4 donor set was prepared by Schiff base condensation of 2-hydroxyimino-3-pentanone and 1,4-diaminobutane in two ways: in protic and in aprotic solvent. Higher yield of (LH2) imine was obtained when the synthesis was carried out using protic solvent (C2H5OH) instead of aprotic benzene (78% and 30%, respectively). Cu(II) metal complex of diimine-dioxime was synthesized in CH3OH from metal salt and LH2 in mole ratio 1:1. The isolated complex was characterized by the elemental analysis, IR spectroscopy and cyclic voltammetry. The structure of [Cu2(LH)2]?(ClO4)2 was determined by the single-crystal X-ray diffraction analysis. Comparison with the structurally related diimine-dioxime Cu(II) complexes revealed the influence of the weak Cu???O(perchlorate) interaction on the geometry of the metallocycle.

Thermolysis of 2-acyloxy-Δ3-1,3,4-oxadiazolines. Evidence for a preferred sense of cycloreversion to carbonyl ylides and for fast 1,4-sigmatropic ylide rearrangement

1989 ◽  
Vol 67 (11) ◽  
pp. 1753-1759 ◽  
Author(s):  
Michael W. Majchrzak ◽  
John Warkentin
Keyword(s):  
Alkyl Group ◽  
Steric Effect ◽  
Benzene Solution ◽  
Sigmatropic Rearrangement ◽  
Acetoxy Group ◽  
High Yield ◽  
Enol Ethers ◽  
Carbonyl Ylide

Thermolysis of 2-acyloxy-2,5,5-trialkyl-Δ3-1,3,4-oxadiazolines in benzene solution at 80 °C furnishes acyloxy-substituted enol ethers (hemiacylals) in high yield. Mixtures of cis:trans isomers of such oxadiazolines afford mixtures of isomeric hemiacylals in nearly the same ratio. Those and other results are rationalized in terms of cycloreversion of the oxadiazolines to carbonyl ylides that are not equilibrated during their lifetimes and undergo primarily 1,4-sigmatropic H-migration. Some fragmentation of the ylides to anhydrides and carbenes was also observed. A consistent mechanistic account includes concerted suprafacial (4π + 2π) cycloreversion in the sense that places a large ylide substituent at C-1 or at C-3, preferentially exo. A smaller preference for the cycloreversion that places the acetoxy group at C-1 in the endo position, when the steric effect of the alkyl group at C-1 is small, can be inferred. The possibility that the overall 1,4-H shift is the result of sequential 1,7-antarafacial and 1,4-suprafacial shifts, in some cases, is considered. Keywords: carbonyl ylide; 1,4-sigmatropic rearrangement; cycloreversion, thermal, of oxadiazolines; ylide, carbonyl; oxadiazoline, thermolysis of.

scholarly journals Theoretical Investigation of Solvation Effects on the Tautomerism of Maleic Hydrazide

2012 ◽  
Vol 9 (1) ◽  
pp. 107-112 ◽  
Author(s):  
Meisam Shabanian ◽  
Hassan Moghanian ◽  
Mohsen Hajibeygi ◽  
Azin Mohamadi
Keyword(s):  
Gas Phase ◽  
Polar Solvent ◽  
Maleic Hydrazide ◽  
Aprotic Solvent ◽  
Dipole Moments ◽  
Structural Data ◽  
Protic Solvent ◽  
Polar Aprotic Solvent ◽  
Pcm Model ◽  
Nbo Charges

A DFT study is used to calculate structural data of tautomers of maleic hydrazide (MH) in the gas phase and selected solvents such as benzene (non-polar solvent), tetrahydrofuran (polar aprotic solvent) and methanol (protic solvent), dimethyl sulfoxide (polar aprotic solvent) and water (protic solvent) using PCM model. All tautomers are optimized at the B3LYP/6−31++G(d,p). The results show that the tautomer MH2except in methanol is more stable than the other tautomers but in methanol MH5(Diol) is more stable. In addition, stability of the tautomers in deferent solvents shows interesting results. Variation of dipole moments and NBO charges on atoms in the solvents were studied.

Solvation of Ions. V. Rates of SN2 Reactions in Mixtures of Protic and Dipolar Aprotic Solvents

1963 ◽  
Vol 16 (4) ◽  
pp. 585 ◽  
Author(s):  
AJ Parker
Keyword(s):  
Aprotic Solvent ◽  
Chloride Ion ◽  
Solvent Mixtures ◽  
Protic Solvent ◽  
Dipolar Aprotic Solvent ◽  
Sn2 Reactions ◽  
Protic Solvents ◽  
Bonding Interaction ◽  
Solvation Of Ions ◽  
Dipolar Aprotic Solvents

The rates of reaction of methyl iodide with chloride ion in some protic-dipolar aprotic solvent mixtures have been measured. The rate-retarding effect of protic solvents at M concentration in dimethylacetamide is in the order p-NO2C6H4OH > C6H5OH > C6H5SH > C6H5CO2H ≈ CH3OH > C6H5NH2 >H2O ≈ D2O. Protic solvents slow the reaction by a general rather than a specific hydrogen bonding interaction with the anion. Both the dipolar aprotic solvent and the protic solvent, as well as the anion, accept hydrogen bonds, and this influences the interaction between protic solvent and anion.

AROMATIC SUBSTITUTION: PART I. THE REACTION OF PHENYLLITHIUM WITH 3-ALKYLPYRIDINES. STERIC EFFECT AND QUANTITATIVE ANALYSIS OF ISOMER RATIOS

1962 ◽  
Vol 40 (2) ◽  
pp. 213-219 ◽  
Author(s):  
R. A. Abramovitch ◽  
Choo-Seng Giam
Keyword(s):  
Quantitative Analysis ◽  
Vapor Phase ◽  
Alkyl Group ◽  
Steric Effect ◽  
Main Product ◽  
Methyl Ethyl ◽  
Aromatic Substitution

No 4-phenylpyridine is formed in the reaction of phenyllithium with pyridine. When phenyllithium reacts with a 3-alkylpyridine the main product is the 3-alkyl-2-phenylpyridine if the alkyl group is methyl, ethyl, or isopropyl, but it is the 5-alkyl-2-phenylpyridine when the substituent is t-butyl. Methods are described for the separation and quantitative analysis of mixtures of 3-alkyl- and 5-alkyl-2-phenylpyridines using vapor phase chromatography. The results are discussed briefly and possible explanations of the observed orientations are mentioned.

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