CCVI.—The Friedel-Crafts' reaction. Part III. Migration of alkyl groups in the benzene nucleus

Reactions of R2,R3-alkyl substituted 2-hydroxybenzenecarboxylic acids 2-HO-C6H2R2-COOH with Grignard reagents R1MgBr in the presence of nickel give stable aryl alkyl ketyl radicals 2-O--R2-, R3-C6H2-CO--R1 where R1 = CH3, C2H5, C2D5, n-C3H7 and R2,R3 = CH3, C2H5, i-C3H7, t-C4H9. The β protons of ketyl group are equivalent (splitting constant 1.25 mT) and non-equivalent (splitting constants within 0.5 to 1.5 mT) for R1 = methyl and other alkyl groups, respectively. Interaction of the γ protons with the unpaired electron was only observed in the case of R1 = n-propyl (splitting constants about 0.07 mT). The substituents R1 have but slight effect on values of splitting constants of the protons in R2,R3 and vice versa. Also splitting constants of the benzene nucleus (a4H = 0.55 mT, a6H = 0.44 mT) are only slightly affected by the substituents R1,R2,R3, which indicates dominant electron-donor effect of the oxido-anion group eliminating the relatively smaller contributions of the alkyl substituents.

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Ionic and Radical Mechanisms in Olefinic Systems, with Special Reference to Processes of Double-Bond Displacement, Vulcanization and Photogelling

Rubber Chemistry and Technology ◽

10.5254/1.3543163 ◽

1942 ◽

Vol 15 (4) ◽

pp. 774-779

Author(s):

Ernest Harold Farmer

Keyword(s):

Double Bond ◽

Special Reference ◽

Methyl Substituent ◽

Benzene Nucleus ◽

Methyl Group ◽

Unsaturated System ◽

Alkyl Groups ◽

Electron Release

Abstract The α-methylenic reactions discussed in the preceding two papers recall a series of interesting observations by Baker and Nathan, which indicate that a p-methyl substituent attached to the benzene nucleus can permit electron release to the nucleus in a manner that appears only in lesser degree in higher alkyl groups, and may be absent in some (e.g., Buγ). Thus in p-methylbenzyl bromide, the suggested function of the methyl group (dotted arrows in (I) permits (see PDF for diagram) additional electron release at the C—Br bond, and so facilitates the anionization of the bromine. Baker and Nathan suggest that the electrons of the duplet constituting the C—H bond of the methyl group are less localized than those in a similarly placed C—C bond, and hence that a methyl group attached to the necessary conjugated unsaturated system is capable of electron-release by a mechanism similar to the tautomeric effect:

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366. Hydrolysis of arylsulphuric acids. Part IV. (a) Conjugation between the benzene nucleus and unsaturated side chains. (b) Steric effects and the influence of alkyl groups.

Journal of the Chemical Society (Resumed) ◽

10.1039/jr9360001654 ◽

1936 ◽

pp. 1654 ◽

Cited By ~ 7

Author(s):

G. Norman Burkhardt ◽

Charles Horrex ◽

Doreen I. Jenkins

Keyword(s):

Steric Effects ◽

Side Chains ◽

Benzene Nucleus ◽

Alkyl Groups ◽

Hydrolysis Of

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Substituted Terminal Alkyl Groups and Their Prospects in Liquid Crystal Chemistry

Molecular Crystals and Liquid Crystals ◽

10.1080/00268948608084954 ◽

1986 ◽

Vol 131 (3) ◽

pp. 353-360 ◽

Cited By ~ 1

Author(s):

Maged Osman

Keyword(s):

Liquid Crystal ◽

Crystal Chemistry ◽

Alkyl Groups

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Electrochemical Vicinal Difluorination of Alkenes: Sustainable, Scalable, and Amenable to Electron-rich Substrates

10.26434/chemrxiv.9974687 ◽

2019 ◽

Author(s):

Sayad Doobary ◽

Alexi Sedikides ◽

Henry caldora ◽

Darren poole ◽

Alastair Lennox

Keyword(s):

Bioactive Compounds ◽

Hypervalent Iodine ◽

Electrochemical Generation ◽

Oxidative Decomposition ◽

Alkyl Groups ◽

Rich Functionality

Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and F conformation. The oxidative difluorination of alkenes represents an H important strategy for their preparation, yet current methods are limited in their alkene-types and tolerance of electron-rich, readily oxidized functionalities, as well as in their scalability. Herein, we report a method for the difluorination of a number of unactivated alkene-types that is tolerant of electron-rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator (in the presence of nucleophilic fluoride and HFIP) using an ‘ex-cell’ approach, which avoids the oxidative decomposition of the substrate. The more sustainable conditions give good to excellent yields of product in up to decagram scales<br>

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Molecular Engineering of Liquid Crystal Polymers by Living Polymerization. 13. Synthesis and Living Cationic Polymerization of 4-((S(-)-2- Methyl-1-Butyl)Oxycarbonyl)-4'-(omega-Oxyalkyl-1-Vinyl Ether)Biphenyl with Undecanyl and Hexyl Alkyl Groups

10.21236/ada235791 ◽

1991 ◽

Author(s):

V. Percec ◽

Q. Zheng ◽

M. Lee

Keyword(s):

Liquid Crystal ◽

Vinyl Ether ◽

Cationic Polymerization ◽

Living Polymerization ◽

Molecular Engineering ◽

Liquid Crystal Polymers ◽

Living Cationic Polymerization ◽

Alkyl Groups

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Kinetics of the Imidazolium Ring-Opening of mRNA 5'-cap Analogs in Aqueous Alkali

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20060567 ◽

2006 ◽

Vol 71 (4) ◽

pp. 567-578 ◽

Cited By ~ 2

Author(s):

Alicja Stachelska ◽

Zbigniew J. Wieczorek ◽

Janusz Stępiński ◽

Marzena Jankowska-Anyszka ◽

Harri Lönnberg ◽

...

Keyword(s):

Electrostatic Interaction ◽

Ring Opening ◽

Nucleophilic Attack ◽

Amino Groups ◽

Hydroxide Ion ◽

Methyl Group ◽

Structural Modifications ◽

Alkyl Groups ◽

Imidazolium Ring ◽

Kinetics Of

Second-order rate constants for the hydroxide-ion-catalyzed imidazolium ring-opening of several mono- and dinucleosidic analogs of mRNA 5'-cap have been determined. Intramolecular stacking of the two nucleobases in the dinucleosidic analogs, m7GpppN (m7G = 7-methylguanosine, N = 5'-linked nucleoside), and electrostatic interaction between the N-alkylated imidazolium ring and phosphate moiety have been shown to shield the m7G moiety against the nucleophilic attack of hydroxide ion. In addition, the effect of methylation of the nucleobase amino groups and replacement of the 7-methyl group with other alkyl groups have been studied. The influence of all the structural modifications studied turned out to be modest, the cleavage rates of the most and least reactive analogs (with the exception of non-phosphorylated nucleosides) differing only by a factor of 5.

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