Eight-membered Rings containing Three or More Heteroatoms

8 Eight-membered Rings containing Three or More Heteroatoms 

5-triazacyclo-octatetraene (423) has been synthesized by the condensation of /7-methoxybiguanidine and benzoylacetone in ethanolic HCl  

Furukawa, Y. Kojima, and S. Hayashi, Chem. and Pharm. Bull. Japan), 1972,20, 927. 

The selenium-containing ring (428) can be prepared by the action of hydrogen selenide on the appropriate amine with formaldehyde in aqueous ethanol,and n.m.r. data reveal that the action of RP(NEt)2 (R = Me, 

4-MeaQH3, or Pr 0) on diethanolamine affords the bicyclic compound (429) rather than (430). 2 The presence of aluminium in an eight-membered ring is postulated in (431), a proposed intermediate in the formation of a trimeric aluminium amide by heating iV-diethylaluminium-AW-diphenylamine. The tetrasulphide (432) is formed, with other compounds, in the reaction shown, and is oxidized to the sulphoxide (433) by peracid the tetra-phosphorus compound (434) has been prepared in 0.3 % yield.  

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