Alkyl 1-[2-(oxido anion)-, 3-, 4-, 5-alkyl substituted]phenyl ketyl radicals

1979 ◽  
Vol 44 (6) ◽  
pp. 1731-1741 ◽  
Author(s):  
Andrej Staško ◽  
Ľubomír Malík ◽  
Alexander Tkáč ◽  
Vladimír Adamčík ◽  
Eva Maťašová
Keyword(s):  
Electron Donor ◽  
Unpaired Electron ◽  
Grignard Reagents ◽  
Slight Effect ◽  
Benzene Nucleus ◽  
Alkyl Groups ◽  
Splitting Constant

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.

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

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:

scholarly journals A versatile method for the N, N-dialkylation of aromatic amines via Grignard reactions on N,N-bis(benzotriazolylmethyl)arylamines

1990 ◽  
Vol 68 (3) ◽  
pp. 456-463 ◽  
Author(s):  
Alan R. Katritzky ◽  
Stanislaw Rachwal ◽  
Jing Wu
Keyword(s):  
Alkyl Group ◽  
Aromatic Amines ◽  
Grignard Reagents ◽  
Grignard Reaction ◽  
Aryl Ring ◽  
Alkyl Groups ◽  
Grignard Reactions ◽  
Stepwise Procedure ◽  
High Yields

Grignard reactions of N,N-bis(benzotriazolylmethyl)arylamines afford the corresponding N,N-dialkylarylamines in high yields. Electron-releasing substituents on the aryl ring facilitate the reaction. Arylamines are N,N-dialkylated with two different alkyl groups by a stepwise procedure: N-benzotriazolylmethylation of an amine followed by a Grignard reaction to introduce the first alkyl group, and repetition of the same procedure to introduce the second alkyl group. Grignard reagents derived from 1,4-dihalobutane, upon reaction with N,N-bis(benzotriazolylmethyl)arylamines, give the corresponding N-aryl-hexahydroazepines together with acyclic products. Keywords: azepine, tertiary arylamines.

scholarly journals Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5’-alkynylation

2017 ◽  
Vol 13 ◽  
pp. 1533-1541 ◽  
Author(s):  
Raja Ben Othman ◽  
Mickaël J Fer ◽  
Laurent Le Corre ◽  
Sandrine Calvet-Vitale ◽  
Christine Gravier-Pelletier
Keyword(s):  
Carbonyl Group ◽  
Protecting Groups ◽  
Grignard Reagents ◽  
Group Effect ◽  
Protecting Group ◽  
Alkyl Groups ◽  
Silyl Groups

The 5’-alkynylation of uridine-derived aldehydes is described. The addition of alkynyl Grignard reagents on the carbonyl group is significantly influenced by the 2’,3’-di-O-protecting groups (R1): O-alkyl groups led to modest diastereoselectivities (65:35) in favor of the 5’R-isomer, whereas O-silyl groups promoted higher diastereoselectivities (up to 99:1) in favor of the 5’S-isomer. A study related to this protecting group effect on the diastereoselectivity is reported.

Anion radicals of beta diketonates

1983 ◽  
Vol 48 (9) ◽  
pp. 2525-2530 ◽  
Author(s):  
Andrej Staško ◽  
Ľubomír Malík ◽  
Peter Pelikán ◽  
Ján Reguli
Keyword(s):  
Anion Radical ◽  
Methine Proton ◽  
Grignard Reagents ◽  
Indo Calculations ◽  
Splitting Constant ◽  
Anion Radicals

Formation of anion radicals [RCOCHCOR']- with R ≡ R' = Me, i-Pr, t-Bu, and with R = Me, R' = Ph has been observed in reactions of beta diketonates wih Grignard reagents. The splitting constant of the methine proton is 0.26 mT, and that of the methyl protons is 1.2 mT if R ≡ R' = Me. According to INDO calculations the anion radical is stabilized with Ni2+ counterion in tetrahedral arrangement.

Cu-Catalyzed Conjugate Addition of Grignard Reagents to Thiochromones: An Enantioselective Pathway for Accessing 2-Alkylthiochromanones

Synlett ◽  
2018 ◽  
Vol 29 (15) ◽  
pp. 2071-2075 ◽  
Author(s):  
Qingxiong Yang ◽  
Jun Wang ◽  
Shihui Luo ◽  
Ling Meng
Keyword(s):  
Conjugate Addition ◽  
Grignard Reagents ◽  
Established Method ◽  
Alkyl Groups ◽  
Biological Studies ◽  
First Time

The enantioselective incorporation of alkyl groups in thiochromones was realized for the first time by a Cu/(R,S)-PPF-P t Bu2-catalyzed conjugate addition of Grignard reagents to thiochromones. With this method, a series of 2-methylthiochromanones were obtained in good yields (up to 96% yield) with moderate-to-good ee values (up to 87% ee). The established method expedites the synthesis of a large library of chiral thiochromanones for further synthetic applications and biological studies.

An EPR and MS Investigation of Hexa-Substituted Pyrrolidine-l-oxyl Aminoxyl Stable Radicals. Unexpectedly Large y-Hydrogen Splittings

1995 ◽  
Vol 50 (10) ◽  
pp. 1531-1536 ◽  
Author(s):  
Yong-Kang Zhang ◽  
Edward G. Janzen
Keyword(s):  
Alkyl Group ◽  
Spin Labels ◽  
Substitution Pattern ◽  
Alkyl Groups ◽  
Fragmentation Mechanisms ◽  
Hyperfine Splitting Constant ◽  
Nitroxide Spin Labels ◽  
Splitting Constant ◽  
First Time ◽  
Aminoxyl Radicals

The y-hydrogen hyperfine splitting constant (γ-H hfsc) for stable aminoxyl (nitroxide) spin labels such as 2,2,5,5-tetramethylpyrrolidine-1-oxyl and their derivatives is usually very small (<1.0 G) and not distinguished with EPR spectrometry. Surprisingly, large γ-H hfsc’s (≥2 .0 G) have been detected with EPR for the first time from ten 2-alkyl-2-phenyl-3,3,5,5- tetramethylpyrrolidine-1-oxyl stable aminoxyl radicals. It is discovered that γ-H hfsc’s are very sensitive to the size and the substitution pattern of 2-alkyl groups. When the 2-alkyl group is CH3 or CD3, γ-H hfsc’s are not resolved in the EPR spectra. But if the 2-alkyl group is C2H5, one γ-H hfsc is very large, equal to 4.72 G in C6H6. If the substituent is longer than C2H5, such as n-C3H7, n-C4H9, n-C5H11, n-C6H13 and CH2=CHCH2- substituents, the γ-H hfsc is slightly smaller, equal to 4.59 G. For secondary substituents such as sec-C4H9 and cyclo-C6H11 , the γ-H hfsc decreases to 2.00 G. Intermediate γ-H hfsc’s correspond to C6H5CH2 (3.18 G) or a tertiary alkyl group such as t-C4H9 (3.47 G). Variation of γ-H hfsc’s is based on the change of the pyrrolidine ring conformation which is a result of the 2-alkyl group influence. The structures of these aminoxyl radicals are characterized also with mass spectrometry. Possible MS fragmentation mechanisms are discussed.

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