Oxygen and Sulfur Derivatives

According to the systematic nomenclature these substances were first named l-f-triazolo[d] pyrimidines in compliance with the general principles of the Ring Index/ More recent papers and Chemical Abstracts indexes use the term i -triazolo[4,5-d]pyrimidine (147) in accord with the lUPAC nomenclature. The numbering of substituents when using the last-mentioned name is different from that of the 8-aza analogs. For the formulas of oxygen and sulfur derivatives names derived from the lactim or thiolactim form are almost exclusively in use (in common with the purine derivatives). These derivatives are thus described as hydroxy and mercapto derivatives, respectively. The name 1,2,3,4,6-pentaazaindene is used only rarely for this system. 

The TJV spectra were measured for practically all the numerous derivatives. Beside the analytical application of these to demonstrate the position of the substituent no detailed interpretation was attempted, however. On the whole, they are similar to the spectra of analogous purine derivatives and also display a similar dependence on Despite the fact that the question of structure with regard to the lactim-lactam (or thiolactim-thiolactam) tautomerism has not been studied in detail, it can be assumed that oxygen and sulfur derivatives, at variance with the conventional way of writing the formulas, possess a lactam or thiolactam structure. This is in agreement with the views on the analogous purine derivatives. 

Experimental Thermochemistry of Heterocycles and Their Aromaticity A Study of Nitrogen, Oxygen, and Sulfur Derivatives of Indane and Indene... 

The oxygen derivatives are stable to most oxidants the sulfur derivatives are cleaved by a wide range of oxidants. The oxygen, but not the sulfur, analogs are readily cleaved by acidic hydrolysis. Sulfur derivatives are cleaved under neutral conditions by mercury(II), silver(I), or copper(II) salts oxygen analogs are stable to those conditions. The properties of oxygen and sulfur derivatives are combined in the cyclic 1,3-oxathianes and 1,3-oxathiolanes. 

Table 23 15N NMR chemical shifts for ring nitrogens of azoles and their oxygen and sulfur derivatives...

Other unsaturated nitrogen, oxygen and sulfur derivatives of alkenes are also transformed into monoalkylborane derivatives . ... 

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