1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) is a cyclic urea sometimes used as a polar, aprotic organic solvent. In 1985, Dieter Seebach showed that it is possible to substitute the relatively toxic hexamethylphosphoramide (HMPA) with DMPU.
Anderson, J. C.; Smith, S. C. (1990). "Oxodiperoxymolybdenum(pyridine)-1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (MoO5 · Py · DMPU): A Safer Alternative to MoOPH for the α-Hydroxylation of Carbonyl Compounds". Synlett1990 (2): 107–108. doi:10.1055/s-1990-21003.