Zwitterionic Ring-Opened Oxyphosphonium Species from the Ph<inf>3</inf>P-I<inf>2</inf> Mediated Reactions of Benzo[ d]oxazol-2(3 H)-ones with Secondary Amines

Abstract

Copyright © 2020 American Chemical Society. Instead of the expected substituted 2-aminobenzo[d]oxazoles, relatively stable ring-opened oxyphosphonium betaines were isolated for the first time from the Ph3P-I2-mediated reactions of benzo[d]oxazol-2(3H)-ones with acyclic secondary amines. The structure of one of these compounds was unambiguously confirmed by single-crystal X-ray analysis. Thermolysis of the betaines gave rise to 2-dialkylaminobenzoxazoles with concomitant loss of triphenylphosphine oxide, suggesting their possible role as intermediates in an alternative reaction path.