Molecular rearrangement of pyrazino[2,3-c]quinolin-5(6H)-ones during their reaction with isocyanic acid

A new tetrahydropyrazino[2,3-c]quinolin-5(6H)-ones were prepared from 3-chloroquinoline-2,4(1H,3H)-diones and ethylene diamine. In their reaction with HNCO, an unprecedented molecular rearrangement produced new types of hydantoin derivatives. All prepared compounds are characterized using their 1H, 13C, and 15N NMR spectra and the results of the X-ray analysis are also presented. A proposed mechanism of rearrangement is discussed in this essay.