First synthesis of 2-phosphonylated quinoxaline 1,4-dioxides: an extension to the Beirut reaction

An extension of the Beirut reaction for the preparation of the first members of the 2-phosphonylated quinoxaline 1,4-dioxide series is described. Contrary to their carboxylated equivalents, preparation of these new compounds could not be achieved under basic conditions but required the use of powdered molecular sieves. Good and reproducible yields were obtained only when the initial suspension in THF was transformed into a pasty film by slow evaporation of ca. 90% of the initial solvent volume.