Polarisation by cation formation: a method for influencing the selectivity of radical chlorination

Kollonitsch, J.; Doldouras, G. A.; Verdi, V. F.

doi:10.1039/j29670001093

Cited by 3 publications

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“…In addition, we have considered the effect of each of the respective functional groups NHAc, COOH, and NH 3 + in isolation. To this end, we note that experimental kinetic data are available in the literature for the chlorination of carboxylic acids, but only qualitative trends have been reported for protonated amines, and it appears that N -alkylacetamides have not been investigated in this context.…”

Section: Introductionmentioning

confidence: 98%

“…Early experimental studies of the regioselectivity of the chlorination reactions of amino acids demonstrated that, under strongly acidic conditions, chlorination failed to occur at the αposition but occurred instead at distal positions along the alkyl chains. 4 It was also demonstrated that the α-positions of N-acylated amino acids are resistant to hydrogen-atom abstraction by Cl • . For example, chlorination of N-benzoylvaline methyl ester was found to result exclusively in the β and γ products, with no product derived from the α-position.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Abstraction by Chlorine Atom from Amino Acids: Remarkable Influence of Polar Effects on Regioselectivity

et al. 2011

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Quantum chemistry computations have been used to investigate hydrogen-atom abstraction by chlorine atom from protonated and N-acetylated amino acids. The results are consistent with the decreased reactivity at the backbone α-carbon and adjacent side-chain positions that is observed experimentally. The individual effects of NH(3)(+), COOH, and NHAc substituents have been examined and reveal important insights. The NH(3)(+) group in isolation is found to be deactivating at the α-position, while the acetamido group is activating. For the COOH group, polar effects lead to a contrathermodynamic deactivation of the thermodynamically most favorable α-abstraction. In the N-acetylamino acid, the α-position is deactivated by the combined inductive effect of the substituents and the presence of an early transition structure, again overriding the greater thermodynamic stability of the α-centered radical product. Deactivation of the α-, β-, and γ-positions results in a peculiar stability for amino acids and peptides and their derivatives with respect to radical degradation.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Hydrogen Abstraction by Chlorine Atom from Amino Acids: Remarkable Influence of Polar Effects on Regioselectivity

et al. 2011

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Modern Methods to Prepare Monofluoroaliphatic Compounds

Sharts

Sheppard

2011

Organic Reactions

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Organic fluorine chemistry has been important since the 1930s. The development of fluorine chemistry during World War II is well documented. Fluorine chemistry emerged in the 1950s because of three events: Large‐scale research designed to synthesize fluorine‐containing rockets was initiated. A fluorine atom at a specific site in a steroid molecule was found to enhance beneficial pharmacological effects New analytical techniques evolved (e.g., GC and NMR). There are eight reactions important for preparation of monofluoroaliphatic compounds. Halogen addition to alkenes and alkynes Fluoroalkylamine reagent for replacement of a hydoxy group. Nitrosyl fluoride addition to an activated double bond Hypofluorites for electrophilic fluorination. Inorganic and heteroatom fluorides for replacement of halogen, hydroxyl, or ester groups Hydrogen fluoride for addition Perchloryl fluoride for hydrogen replacement Condensation of a monolfluorinated organic compound.

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Novel Methods for Selective Fluorination of Organic Compounds: Design and Synthesis of Fluorinated Antimetabolites

Kollonitsch

1978

Israel Journal of Chemistry

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Since 1970 we developed three novel methods of fluoro-organic synthesis in our laboratory, namely: photofluorination (R-H -> R-F); fluorodehydrozylation (R-OH -> R-F); fluorodesulfurization (R-SH -> R-F). The general idea suggesting the development of the first two of these reactions was to find one-step methods for transforming readily available and relatively complex organic compounds into the corresponding fluorine derivatives. The third method emerged as a chance discovery in an attempt to photofluorinate penicillamine, an amino acid with an SH group. The primary motivation of our search was to develop straightforward and routine syntheses of fluorine-containing antimetabolites including enzyme inhibitors. Therefore, it was very attractive to find methods of fluorination capable of transforming a metabolite into an antimetabolite in one single step. The general concept that C-ftuorinated metabolites can represent antimetabolites was already established. However, F analogs of metabolites in general were considered probes for understanding the behavior of the desfluoro metabolites rather than compounds of practical use, e.g.

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Polarisation by cation formation: a method for influencing the selectivity of radical chlorination

Cited by 3 publications

References 0 publications

Hydrogen Abstraction by Chlorine Atom from Amino Acids: Remarkable Influence of Polar Effects on Regioselectivity

Hydrogen Abstraction by Chlorine Atom from Amino Acids: Remarkable Influence of Polar Effects on Regioselectivity

Modern Methods to Prepare Monofluoroaliphatic Compounds

Novel Methods for Selective Fluorination of Organic Compounds: Design and Synthesis of Fluorinated Antimetabolites

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