SEVEN-MEMBERED HETEROCYCLIC RINGS FUSED TO BENZENE

SEVEN-MEMBERED HETEROCYCLIC RINGS FUSED TO BENZENE 

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Seven-membered nitrogen-containing heterocycles, especially those fused to benzene rings, are important in drug design. The famous tranquillisers Librium 91 and Valium are based on... 

There are now two possible routes to the final product. Reductive elimination would insert the new alkyne into one of the old C-Co bonds and form a seven-membered ring heterocycle. This could close in an electrocyclic reaction to give the new six-membered ring with the cobalt fused on one side and hence the cobalt complex of the new benzene. 

Benzene-fused seven- and eight-membered ring heterocycles such as I are important compounds in the pharmaceutical industry owing to their effect as cardiovascular agents. Their complex chemistry ought to be, therefore, of some relevance to anyone interested in this broad field of organic chemistry. The present case is an example of the versatile chemistry of these heterocycles. 

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