An alternative approach to differentially substituted 2-oxazoline chalcogen derivatives

In this study we present an alternative method to obtain several substituted mono or bis-2-oxazolines containing a chalcogen atom as a tether element. Alkylation of 2-tosyloximethylene-2-oxazoline with an appropriate sodium, lithium or potassium alkoxide yielded the corresponding ether. Introduction of sulfur or selenium was easily accomplished using the corresponding sodium salts. The 77Se NMR for alkyl or aryl 2-methylene-2-oxazoline selenides shows good correlation with the electronegativity pattern of substituents. Most products containing oxazolinyl-chalcogen were stable under the usual experimental conditions. However, the tellurium derivatives showed unusual sensitivity to light and oxygen, decomposing through a very complex mechanistic pathway. As a result of this oxidative process, 4,4-dimethyl-2-oxazoline-2-carbaldehyde could be isolated and fully characterized for the first time, in 17% yield.