GLYCOLONITRILE OLIGOMERIZATION - STRUCTURE OF ISOLATED OXAZOLINES, POTENTIAL HETEROCYCLES ON THE EARLY EARTH

A study of glycolonitrile polymerization has led to the isolation and characterization of two 2,5-dihydro-4-aminooxazoles, 4 and 5. Previous reports have misassigned these structures as s-triazines or pyrimidin es, X-ray diffraction analysis of crystals of 4 and an acetylated oxaz ole derivative of 5 (6) confirm the proposed structures. Ab initio com putations are used to assess the relative thermodynamic stability of t hree trimer isomers (an s-triazine, an aminohydroxypyrimidine, and an aminooxazoline), and the results indicate that 4 is a novel kinetic pr oduct. Mechanistic considerations rationalize kinetic oxazole formatio n over the more customary triazine or pyrimidine trimers.