N-Amino-2-methoxy-1-azaazulenium salt 2 has been synthesized
from 2-methoxy-1-azaazulene with
O-mesitylenesulfonylhydroxylamine and its structure has been
characterized by X-ray crystal analysis. The salt 2 reacts with ethyl
cyanoacetate in the presence of potassium carbonate in acetonitrile to
give ethyl (1-amino-1,2-dihydro-1-azaazulen-2-ylidene)cyanoacetate 4,
which undergoes cyclization with potassium carbonate in ethanol to give
ethyl 2-amino-3,3a-diazacyclopent[a]azulene-1-carboxylate.
Reaction of 2 with diethyl ethoxymethylenemalonate in the presence of
potassium carbonate in acetonitrile gives ethyl
2-methoxy-2a,3-diazabenz[cd]azulene-5-carboxylate and ethyl
3,3a-diazacyclopent[a]azulene-1-carboxylate as cyclization
products. Cycloaddition of the salt 2 with an acetylenic ester proceeds
regioselectively and gives 3,3a-diazacyclopent[a]azulene
derivatives and 2a,3-diazabenz[cd
![](https://www.rsc.org/images/entities/char_200a.gif)
]azulene
derivatives.
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