Oxazoles physicochemical properties

This chapter is an attempt to present the important results of studies of the synthesis, reactivity, and physicochemical properties of this series of compounds. The subject was surveyed by Bulka (3) in 1963 and by Klayman and Gunther (4) in 1973. Unlike the oxazoles and thiazoles. there are few convenient preparative routes to the selenazoles. Furthermore, the selenium intermediates are difficult to synthesize and are often extremely toxic selenoamides tend to decompose rapidly depositing metallic selenium. This inconvenience can be alleviated by choice of suitable reaction conditions. Finally, the use of selenium compounds in preparative reactions is often complicated by the fragility of the cycle and the deposition of metallic selenium. 

The physicochemical properties of oxazoles to 1972 have been comprehensively reviewed by Lakhan and Ternai (3) whose work constitutes a point of departure for this section. Mention is made here only of those properties relevant to the detection, isolation, structure elucidation, and behavior of the natural compounds. The oxazole moiety in nature is usually embedded in a variety of functionality, and the rather innocuous properties of the parent molecule do not dominate or influence the behavior of the oxazole alkaloids to the extent that these compounds can be collectively regarded as displaying any characteristic set of physicochemical properties. Table III lists the physical and spectral properties of the compounds covered in this chapter. 

Among systems with two and more various heteroatoms in the ring, thiazole, oxazole, and their derivatives attract attention because of the interesting physicochemical properties and significant biological activity... 

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