Abstract
New 2-chloromethyl-6-halogeno-imidazo[1,2-a]pyridines and 2-chloromethyl-6-halogeno-3-nitroimidazo[1,2-a]pyridines were prepared and reacted under experimental conditions of S RN 1 reactions with different sulfur and carbon centered nucleophiles to give new 6-halogeno-2-substituted-imidazo[1,2-a]pyridines and 6-halogeno-3-nitro-2-substituted-imidazo[1,2-a] pyridines in good yields. Only the chloromethyl group was found to be reactive under these experimental conditions.
Highlights
Substitution reactions at an sp[3] carbon atom of the reductive alkylating agents, p-nitrobenzyl chloride or 2-halogeno-2-nitropropane, which proceed via a chain multi-stage sequence involving radical anions and free radicals as intermediates were first proposed independently by Kornblum[1] and Russell[2] in 1966
Among the heterocyclic analogues of o-nitrobenzyl derivatives which react by SRN1 reactions, our group has reported the SRN1 reactions of nitronate anions with a series of imidazoles fused to a heterocyclic ring bearing the chloromethyl group ortho to the nitro group
SRN1 displacements of aromatic substrates by sulfur nucleophiles can be achieved in DMSO with different types of initiation,[3] the PhSO2- anion has not been reported to react
Summary
Substitution reactions at an sp[3] carbon atom of the reductive alkylating agents, p-nitrobenzyl chloride or 2-halogeno-2-nitropropane, which proceed via a chain multi-stage sequence involving radical anions and free radicals as intermediates were first proposed independently by Kornblum[1] and Russell[2] in 1966. With photostimulation in DMSO in presence of 2 equivalents of the sodium salt of benzenesulfinic acid, 3a and 3b react probably following an SN2 mechanism only at the chloromethyl group with good yield, respectively 69 and 80%, to give the corresponding sulfones 3c and 3d.
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