Synthesis from N-acyl Selenoureas

2-Aminoselenazoles are crystalline compounds, and with the exception of the nonsubstituted derivative (1) they are stable and practically odorless. They are more basic than 2-aryl- or 2-alkylselenazoles. The hydrochlorides are not easily hydrolyzed in aqueous solution. Some of the K-substituted compounds are oily liquids. 

The 5-position of 2-diethylamino-4-methylselenazole is very reactive. Thus it can undergo coupling with phenyldiazonium chloride or even nitration under mild conditions. 

2-Amino-4-aryl-5-acetic acid selenazoles were used by Knott (2l i as intermediates in the preparation of T.2, 4.6-naphthoselenazoles (21. 30, 31). 

From the point of view of reactivity, there is little difference betvv een 2-amino-selenazoles and aryl- Or alkyl-2-aminoselenazoles, except that the A -arvl derivatives are generallv less basic and that their salts are more easily hydrolyzed. 

If in the Hantzsch s synthesis, selenoamide is replaced by a selenosemi-carbazide (HjJN -NH-CSe-l ). condensation can take place upon 

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