A facile, one-pot synthesis of multisubstituted quinoxalin-2(1H)-ones via a Ugi 4CR/catalytic aza-Wittig sequence has been developed. In the presence of a catalytic amount of 3-methyl-1-phenyl-2-phospholene 1-oxide, the reaction of 2-aminobenzoyl azides, aldehydes, ketoacids, and isocyanides selectively produces quinoxalin-2(1H)-o...