THE USE OF 2-OXAZOLIDINONES AS LATENT AZIRIDINE EQUIVALENTS .2. AMINOETHYLATION OF AROMATIC-AMINES, PHENOLS, AND THIOPHENOLS

The utility of 2-oxazolidinones 1 as latent, carboxylated aziridine functionalities was examined. Reaction of 2-oxazolidinone (1a), 3-methyl-2-oxazolidinone (1b), 3-(phenylmethyl)-2-oxazolidinone (1c), 3-phenyl-2-oxazolidinone (1d), 4,4-dimethyl-2-oxazolidinone (1e), and 5-ethyl-2-oxazolidinone (1f) with aromatic amine salts, phenol, or thiophenols at elevated temperatures (> 130-degrees-C) afforded aminoethylated adducts. The aminoethylation occurred with concomitant loss of carbon dioxide to furnish variously substituted N-aryl-1,2-ethanediamines 4, 1-(2-phenoxyethyl)-2-imidazolidinone (8), or 2-(arylthio)ethanamines 9 on reactions of 1 with aromatic amine salts, phenol, and thiophenols, respectively. Imidazolidinone 8 is believed to be a secondary reaction product resulting from the condensation of the initially formed 2-phenoxyethanamine with starting oxazolidinone 1a. The aminoethylation reaction did not proceed with aliphatic amine hydrochlorides or alkyl mercaptans. Preliminary mechanistic pathways for these ring openings were also investigated employing a specific, C-5 deuterium-labeled oxazolidinone 1b-d2. Ring-opening experiments of 1b-d2 with N-methylaniline hydrochloride suggest reaction can occur through either a dioxazolinium 5 and/or an aziridinium 6 intermediate. In contrast, reaction of 1b-d2 with thiophenol suggests ring-opening to proceed only via the dioxazolinium pathway.