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Copper(I) Chloride Mediated Amination of Halobenzenes via Azides: Scope, Mechanistic Aspects, and C–C Cleavage Reactions

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posted on 2023-01-20, 20:20 authored by Max Roemer, Nicholas Proschogo, Ian Luck
Selective azidation–amination of long-chain alkanoyl halobenzenes with sodium azide, promoted by copper(I) chloride, is reported. The protocol is, apart from CuCl and NaN3, additive free and allows the isolation of versatile amine–azides. Alkyl cleavage occurs as a side reaction through an unusual Schmidt-type azide insertion adjacent to the carbonyl group, forming alkyl nitriles possibly via radical pathways. Mechanistic studies involving 15N labeling experiments and test substrates indicate that the reaction occurs via 1-azido-4-alkanoyl benzenes. The amination is applicable for substrates with electron-withdrawing groups and proceeds under mild conditions. The mechanism of the amine formation involves nitrenes. Intermediates were trapped by carrying out the reaction in the presence of the 2,2,6,6-(tetramethylpiperidin-1-yl)oxyl stable radical and characterized by high-resolution mass spectrometry. The intermediates are consistent with earlier mechanistic proposals.

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