Zwitterionic ring-opened oxyphosphonium species from the Ph3P-I2 mediated reactions of benzo[d]oxazol-2(3H)-ones with secondary amines.

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.