Microwave-assisted synthesis of benzo[b]phosphole oxide derivatives by oxidative addition of acetylenes and secondary phosphine oxides or alkyl phenyl-H-phosphinates

Abstract

A new and practical microwave (MW)-assisted method was developed for the fast and efficient oxidative addition of secondary phosphine oxides or alkyl phenyl-H-phosphinates and acetylenes. The reaction was optimized in respect of the oxidative agent, the reaction time, the temperature and the molar ratio of the starting materials. The protocol developed enabled the synthesis of novel benzo[b]phosphole oxide derivatives under mild conditions for a short reaction time. By the use of special reagents, such as alkyl phenyl-H-phosphinates or ethyl phenylpropiolate, reactive groups (phosphinic acid ester and carboxylic ester) could be integrated into the benzophosphole skeleton, which may be further functionalized towards various synthetic directions, therefore, fine-tuning the optical properties of the target molecules. The crystal structure of a benzo[b]phosphole oxide derivative was investigated by X-Ray diffraction, which gave structural information about the compound and its molecular interactions in the crystal.