Abstract
1-(2-Chloroethyl)-(IIa), 1-isopropyl-(IIb), 1-isobutyl- (IIc) and 1-cyclohexyl-1-nitroso-3-(3-pyridylmethyl) urea (IId) isomerized to the corresponding 3-nitroso isomers (IIIa-d) in formic acid. This type of rearrangement was also observed in acetic acid, 10% hydrochloric acid, 10% sulfuric acid, methanol saturated with hydrogen chloride, and thionyl chloride. However, 1-isopropyl- (IIIb) and 1-cyclohexyl-3-nitroso-3-(3-pyridylmethyl) urea (IIId), in which the N1 substituents are bulky, hardly isomerized to the 1-nitrosoureas (IIb, d). Transnitrosation of 1-(2-chloroethyl)-1-nitroso-3-(3-pyridylmethyl) urea (IIa) with 1-methyl-3-(2-pyridylmethyl) urea gave the denitrosated compound (Ia) and a newly nitrosated compound, 1-methyl-1-nitroso-3-(2-pyridylmethyl) urea (V). It is suggested that this type of rearrangement is an acid-catalyzed, intermolecular rearrangement governed by the steric effect of the N1 substituents.
