Cyclization of (2-Hydroxyethyl) urea Derivatives to Give 3-Nitroso-2-oxazolidinones under Usual Nitrosation Conditions

Treatment of (2-hydroxyethyl) urea derivatives (Ia-e) with sodium nitrite in the presence of acids or with nitrosyl chloride in chloroform gave 3-nitroso-2-oxazolidinones (IIa-e) in 10-77% yields. These 3-nitroso-2-oxazolidinones were denitrosated with hydrogen chloride in methanol to give the corresponding 2-oxazolidinones (IIIa-e) in 35-60% yields. An N, N-disubstituted urea, 1-(2-hydroxyethyl)-1-methylurea (If) also cyclized to give 3-methyl-2-oxazolidinone (IIf) under the same conditions. The mechanism of this type of cyclization is discussed.