ChemInform Abstract: HOMOLYTIC AROMATIC SUBSTITUTION BY ALKYL RADICALS

<p>The monoalkylation of N-methoxypyridinium salts with alkyl radicals generated from alkenes (via hydroboration with catecholborane), alkyl iodides (via iodine atom transfer) and xanthates is reported. The reaction proceeds under neutral conditions since no acid is needed to activate the heterocycle and does not require the use of an external oxidant. A rate constant for the addition of a primary radical to N-methoxylepidinium >107 M–1 s–1 was experimentally determined. This rate constant is more than one order of magnitude larger than the one measured for the addition of primary alkyl radical to protonated lepidine demonstrating the remarkable reactivity of methoxypyridinium salts towards radicals. The reaction could be extended to a three component carbopyridinylation of electron rich alkenes including enol esters, enol ethers and enamides.</p>

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Intramolecular homolytic aromatic substitution of alkyl 2-benzimidazolyl sulfones as a means of entry into alkyl radicals for organic synthesis

Tetrahedron Letters ◽

10.1016/j.tetlet.2008.02.174 ◽

2008 ◽

Vol 49 (18) ◽

pp. 2999-3003 ◽

Cited By ~ 3

Author(s):

David Crich ◽

Daniel Grant

Keyword(s):

Organic Synthesis ◽

Aromatic Substitution ◽

Alkyl Radicals ◽

Homolytic Aromatic Substitution

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Organoboron Mediated Homolytic Aromatic Substitution of N-Methoxypyridinium Salts

10.26434/chemrxiv.14518038.v1 ◽

2021 ◽

Author(s):

Samuel Rieder ◽

Camilo Meléndez ◽

Kleni Mulliri ◽

Philippe Renaud

Keyword(s):

Rate Constant ◽

Aromatic Substitution ◽

Enol Ethers ◽

Alkyl Radicals ◽

Homolytic Aromatic Substitution ◽

Reaction Proceeds ◽

Order Of Magnitude ◽

Enol Esters ◽

The One ◽

Neutral Conditions

<p>The monoalkylation of N-methoxypyridinium salts with alkyl radicals generated from alkenes (via hydroboration with catecholborane), alkyl iodides (via iodine atom transfer) and xanthates is reported. The reaction proceeds under neutral conditions since no acid is needed to activate the heterocycle and does not require the use of an external oxidant. A rate constant for the addition of a primary radical to N-methoxylepidinium >107 M–1 s–1 was experimentally determined. This rate constant is more than one order of magnitude larger than the one measured for the addition of primary alkyl radical to protonated lepidine demonstrating the remarkable reactivity of methoxypyridinium salts towards radicals. The reaction could be extended to a three component carbopyridinylation of electron rich alkenes including enol esters, enol ethers and enamides.</p>

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