Abstract
A facile, green, and efficient method for the direct oxidative amination of benzoxazoles using heterocyclic ionic liquid as catalyst has been developed. The reaction proceeded smoothly at room temperature and gave the desirable 2-aminobenzoxazoles with good to excellent yields (up to 97%). The catalyst 1-butylpyridinium iodide can be easily recycled and reused with similar efficacies for at least four cycles.
Highlights
Amino-substituted azoles and their derivatives are ubiquitous in functional materials, pharmaceuticals, and natural products [1,2,3]
In the presence of 5 mol% [BPy]I, 1.5 equiv. of tert-butyl hydroperoxide (TBHP), and 3 equiv. of acetic acid, the acid, the reaction of 1a and 2a was proceeded at room temperature for 7 h to give reaction of 1a and 2a was proceeded at room temperature for 7 h to give 2-morpholinobenzo[d]oxazole
All of the above results indicate that the activation of the morpholine (2a) via in situ preparation of a highly reactive N-I bond from [BPy]I and TBHP seems plausible
Summary
Amino-substituted azoles and their derivatives are ubiquitous in functional materials, pharmaceuticals, and natural products [1,2,3]. The development of effective methods to synthesize these compounds has attracted great attention In this regard, direct C–H amination reaction displaying an advantage in atom efficiency has been pioneered by Cho (Scheme 1a), Monguchi, Wang, Kawano, Miyasaka, Xie and others in the past decade [8,9,10,11,12,13,14,15,16,17,18,19,20]. These catalytic systems effectively overcome some drawbacks of approaches still suffer from minor drawbacks, such as high temperature, long reaction time, and using stoichiometric amounts of hypervalent iodine compounds
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