A convenient preparation of 3H‐1,3‐Oxazol‐2‐One and its N‐formyl derivative

Abstract

AbstractThe electrochemical hydroxylation of 1,3‐oxazolidin‐2‐one to 4‐hydroxy‐1,3‐oxazolidin‐2‐one is reported; a substantial side product is the symmetrical ether derived from the hydroxycompound. An improved synthesis of 3H‐1,3‐oxazol‐2‐one has been developed; nothing more is involved than boiling the readily available 4‐methoxy‐1,3‐oxazolidin‐2‐one with an excess of acetic acid and one equivalent of acetic anhydride, evaporation of the solvents and recrystallization of the residue. The mechanism of the reaction is discussed. In a reinvestigation of the known conversion, by acetic anhydride, of 4‐methoxy‐1,3‐oxazolidin‐2‐one to N‐acetyl‐1,3‐oxazol‐2‐one, we have uncovered the formation of two 3,4′‐bioxazole side products [3‐(2‐oxo‐1,3‐oxazolidin‐4‐yl) 1,3‐oxazol‐2‐one and its N‐acetyl derivative], especially in the presence of added acids. We have found that N‐formyl‐1,3‐oxazol‐2‐one can be made in good yield by treatment of 3H‐1,3‐oxazol‐2‐one with a mixture of formic acid and acetic anhydride (“acetic formic anhydride”) in the presence of 4‐(N, N‐dimethylamino)pyridine; the formation of an intermediate phosphonate derived from 3H‐1,3‐oxazol‐2‐one, as described in the literature synthesis of N‐formyl‐1,3‐oxazolone, is superfluous.