Unexpected Reactivity of o-Nitrosophenol with RCH2Br: C−H Bond Cleavage and Annulation to Benzoxazoles and Benzoxazines (R = Alkynyl)

A one-pot reaction between two molecules of 5-diethylamino-2-nitrosophenol with one molecule of 2-butynyl bromide gave rise to a new heterocyclic compound (structure shown above) consisting of one benzoxazole and one benzoxazine ring. The reaction works equally well with 1-phenyl-3-chloro-1-propyne. It was also found that 5-diethylamino-2-nitrosophenol reacts with R-CH2Br (R = aryl or vinyl) to give benzoxazoles with good functional group tolerance and high yield.