Reactions of Hindered α-Substituted Acids. V. The Effect of a β-Methyl Group on the Acid-Catalyzed Rearrangement1,2

1957 ◽  
Vol 79 (21) ◽  
pp. 5777-5780
Author(s):  
Wyman R. Vaughan ◽  
A. Charles Schoenthaler
Keyword(s):  
Methyl Group ◽  
Acid Catalyzed

Deuterium exchange of C-methyl protons in lumazine derivatives

1970 ◽  
Vol 48 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. McAndless ◽  
Ross Stewart
Keyword(s):  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Acid Catalysis ◽  
Deuterium Exchange ◽  
Base Catalysis ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
General Base ◽  
General Acid ◽  
Acid Catalyzed

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of 3, acid-catalyzed addition of water across the C6—N5 double bond.

Acid-catalyzed rearrangements of an A(1)-nor-triterpenoid 2α,3α-epoxide

1989 ◽  
Vol 54 (2) ◽  
pp. 413-429 ◽  
Author(s):  
Jiří Klinot ◽  
Jiří Liška ◽  
Alena Forgáčová ◽  
Miloš Buděšínský ◽  
Jiří Protiva ◽  
...  
Keyword(s):  
Acidic Medium ◽  
Boron Trifluoride ◽  
Mass Spectra ◽  
Boron Trifluoride Etherate ◽  
Methyl Group ◽  
Unsaturated Alcohols ◽  
Acid Catalyzed ◽  
C Nmr

Reactions of 2α,3α-epoxide X, derived from 19β,28-epoxy-A(1)-nor-18α-oleanane, with acids proceed with migration of the 10β-methyl group into the position 2β, giving rise to unsaturated alcohols XII and XIV and diene IX. Reaction with boron trifluoride etherate afforded ketone XI in addition to XII and XIV. Olefin VIII rearranged in acidic medium to give olefins XXVI and XXVII. The rearranged products were converted into other derivatives and their structure was established by 1H and 13C NMR, IR, UV and mass spectra.

Kinetics of acid-catalyzed cyclization of substituted hydantoinamides to substituted hydantoins

1987 ◽  
Vol 52 (8) ◽  
pp. 1999-2004 ◽  
Author(s):  
Jaromír Kaválek ◽  
Vladimír Macháček ◽  
Gabriela Svobodová ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrogen Atom ◽  
Nitrogen Atom ◽  
Hydrochloric Acid ◽  
Dissociation Constants ◽  
Amide Group ◽  
The Other ◽  
Methyl Group ◽  
Acid Catalyzed ◽  
Cyclization Rate ◽  
Kinetics Of

The kinetics of acid-catalyzed cyclization of the hydantoinamides type R3-N(5)H-CO-N(3)R2-CH2-CO-N(1)HR1 (R1, R2, R3 = H and/or CH3) has been studied in 0·5 to 5 mol l-1 hydrochloric acid. The cyclization rate is limited by the rate of the attack of nitrogen atom N(5) on the carbon atom of the protonated amide group. The dissociation constants of the protonated hydantoinamides and rate constants of their cyclizations have been determined. Replacement of hydrogen atom by methyl group at the N(5) nitrogen atom accelerates the cyclization about two times., the same substitution at N(3) accelerates about 50x, whereas at N(1) it results in a 300 fold retardation. With the hydantoinamides having R3 = CH3, the cyclization rate of the protonated hydantoinamide increases with increasing concentration of hydrochloric acid, whereas with the other derivatives this value is independent of the acid concentration.

Stereochemistry of acid-catalyzed cleavage of 7-chloro-1-methylnortricyclene in deuterated medium; evidence for edge protonation of nortricyclenes

1980 ◽  
Vol 58 (16) ◽  
pp. 1725-1737 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Frank Peter Cappelli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spectroscopic Analysis ◽  
Methyl Group ◽  
Magnetic Resonance Spectroscopic Analysis ◽  
Acid Catalyzed ◽  
Nuclear Magnetic

Cleavage of 7-chloro-1-methylnortricyclene (1e) in D2SO4–DOAc yields deuterated syn-7-chloro-1-methyl-exo-2-norbornyl acetate (3a-d) (1.04 excess d per molecule) and deuterated anti-7-chloro-1-methy l-exo-2-norbornyl acetate (3b-d) (1.28 excess d per molecule) as the kinetic products. 1H and 2H nuclear magnetic resonance spectroscopic analysis of the corresponding alcohols complexed with Eu(fod)3 shows that deuterium is located endo at C-6 and in the methyl group of the syn-7-chloroacetate, endo at C-6 and C-2, at C-7, and in the methyl group of the anti-7-chloroacetate. That the deuterium at C-6 of both acetates is 80–90% stereochemically pure endo, in our view, establishes that the bond farthest removed from the electron-withdrawing chlorine is preferentially cleaved via edge deuteronation.

Synthesis, base strength, and prototropic behaviour of a number of alkyllumazines

1985 ◽  
Vol 63 (12) ◽  
pp. 3290-3293 ◽  
Author(s):  
Ross Stewart ◽  
S. J. Gumbley
Keyword(s):  
Sulfuric Acid ◽  
Isotopic Exchange ◽  
The Other ◽  
Methyl Groups ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Neutral Compounds ◽  
Protonated Forms ◽  
Base Strength ◽  
Acid Catalyzed

A number of lumazines and 5-deazalumazines containing a methyl group at C-7 have been prepared, their pKBH+ values determined, and measurements made of the rates at which the hydrogen atoms of their 7-methyl groups undergo isotopic exchange in aqueous sulfuric acid. The presence of an alkyl group at N-8 in the protonated forms of these compounds activates the neighbouring methyl group at C-7; the effect is considerably larger than that previously observed for a methyl group at C-6, which is the other neighbouring position. The comparison of methyl and hydrogen at N-8 can be made only for the acid-catalyzed reaction because the structures of the neutral compounds, which take part in the base-catalyzed reaction, are not analogous.

Notizen: Specific Acid Catalyzed Deuteration of the Acetyl Groups of 2,4-Diacetyldeuterohemin-OMe

1975 ◽  
Vol 30 (3-4) ◽  
pp. 288-289 ◽  
Author(s):  
Oskar Oster ◽  
George W. Neireiter ◽  
Frank R. N. Gurd
Keyword(s):  
Protoporphyrin Ix ◽  
Methyl Group ◽  
Acid Catalyzed

The methyl group of the acetyl groups in 2,4-diacetyldeuterohemin-OMe has been selectively deuterated. After removal of the iron, D6-2,4-diacetyl-deuteroporphyrin-OMe can be reduced to the corresponding hematoporphyrin and subsequent dehydration gives deuterated vinylic groups for protoporphyrin IX–OMe.

Vinyl ether hydrolysis XXVIII. The mechanism of reaction of methyl α-(2,6-dimethoxyphenyl)vinyl ether

1993 ◽  
Vol 71 (1) ◽  
pp. 38-41 ◽  
Author(s):  
J. Jones ◽  
A. J. Kresge
Keyword(s):  
Vinyl Ether ◽  
Nucleophilic Attack ◽  
Tracer Study ◽  
Solvent Isotope Effect ◽  
Methyl Group ◽  
Hydronium Ion ◽  
Mechanism Of Reaction ◽  
Acid Catalyzed ◽  
Solvent Isotope ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of methyl α-(2,6-dimethoxyphenyl)vinyl ether in aqueous solution at 25 °C occurs with the hydronium ion catalytic coefficient [Formula: see text] and gives the solvent isotope effect [Formula: see text] this indicates that reaction occurs by rate-determining proton transfer from the catalyst to the substrate to generate an alkoxycarbocation intermediate. An oxygen-18 tracer study shows further that, despite the steric hindrance provided by its two ortho substituents, this cation then reacts by addition of water to the cationic carbon atom to generate a hemiacetal, and not by nucleophilic attack of water on the methyl group remote from the carbocationic center:[Formula: see text]

Fate of the Methyl Group in the Sulfuric Acid Catalyzed Oxidation of Toluene to Phenol

1980 ◽  
Vol 19 (3) ◽  
pp. 468-470 ◽  
Author(s):  
James E. Lyons ◽  
George Suld ◽  
Robert W. Shinn ◽  
Chao-Yang Hsu
Keyword(s):  
Sulfuric Acid ◽  
Methyl Group ◽  
Acid Catalyzed ◽  
Catalyzed Oxidation

ortho Diquaternary Aromatic Compounds. IV. Acid-catalyzed Rearrangements of Polyalkyltetralones and Related Ketones

1973 ◽  
Vol 51 (10) ◽  
pp. 1598-1609 ◽  
Author(s):  
Lawrence Ross Coates Barclay ◽  
Robert Hayworth Young ◽  
Keir Leigh Adams ◽  
Helen Mary Foote
Keyword(s):  
Reaction Mechanism ◽  
Quantitative Study ◽  
Ferric Chloride ◽  
Aluminum Chloride ◽  
Aromatic Compounds ◽  
Methyl Group ◽  
Acid Catalyzed ◽  
Acetic Acids

The ketones 1,1,4,4-tetramethyl-2-tetralone (1a), 1,1,4,4,7-pentamethyl-2-tetralone (1b), and 1,1,4,4,6-pentamethyl-2-tetralone (1c) undergo rearrangement on heating with aluminum chloride or ferric chloride in tetrachloroethane or nitromethane into mixtures of their respective isomeric ketones, 1-acetyl-1,3,3-trimethylindane (2a) and 2,2,4,4-tetramethyl-1-tetralone (3a) from 1a, 1-acetyl-1,3,3,6-tetramethylindane (2b) and 2,2,4,4,7-pentamethyl-1-tetralone (3b) from 1b, and 1-acetyl-1,3,3,5-tetramethylindane (2c) and 2,2,4,4,6-pentamethyl-1-tetralone (3c) from 1c. A quantitative study using g.l.c. of the distribution of the ketones with time shows that the sequence of the rearrangement is: [Formula: see text]. A methyl group homologously para to the carbonyl (1c) accelerates the rearrangement. The same kind of rearrangement takes place during Friedel–Crafts cyclialkylation with 2,2,5,5-tetramethyltetrahydrofuranone. A unifying reaction mechanism is postulated to account for the rearrangements. This mechanism also accounts for the rearrangement and fragmentation products from treatment of 1,1,4,4-tetramethyl-2,3-dioxotetralin (9) with aluminum chloride or sulphuric–acetic acids. The products from 9 include 1-acetyl-1,3,3-trimethyl-2-indanone, 1,1,3-trimethyl-2-indanone, and, from the aluminum chloride – catalyzed rearrangement, 5(or 6)-acetyl-1,1,3-trimethyl-2-indanone.

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