M-Chloroperbenzoic acid-oxchromium (VI)-mediated cleavage of 2, 4, 5-trisubstituted oxazoles. Issue 13 (29th March 2017) - Patil, Pravin C.
Graphical abstract: Highlights: A new method for the cleavage of 2, 4, 5-trisubstituted oxazoles to imides and triacylamines is detailed. The oxidation system utilizes two reagents composed of a peroxide and oxochromium (VI). Mechanisms are proposed for the oxidative cleavage reaction. A synthesis of (±)-phoracantholide seco -acid is detailed. Abstract: An array of 2-substituted-4, 5-diphenyloxazoles were found to be cleaved to triacylamines and diacylamines (imides) using a reagent system composed of m -chloroperbenzoic acid (MCPBA) and 2, 2′-bipyridinium chlorochromate (BPCC). The 2-alkyl-4, 5-diphenyloxazoles give imides (38–60%) as the predominant cleavage product while the 2-aryl-4, 5-diphenyloxazoles give triacylamines (44–71%). Two mechanisms involving intermediates such as cyclic endoperoxides or oxachromacycles were proposed. An application of the oxidative cleavage to the multi-step synthesis of (±)-phoracantholide I seco acid is detailed.