Furan 2-ethyl-4-methyl-, ring synthesis

Furans continue to be useful synthons for pyridazine syntheses. A detailed investigation of the reaction between ethyl 2-methoxy-2-methyl-3-oxofuran-4-carboxylate (47) and hydrazines revealed that, depending upon reaction conditions, compound 49, a mixture of 48 and 49 or, in addition to these, also 50, is obtained.172,173 Similarly, ethyl 5-nitrofuran-3-carboxylate and hydrazine yield a pyridazine, probably by addition, ring opening of the furan, and recyclization [Eq. (12)].174 Another synthesis involves electrolytic methoxylation of a furan derivative and subsequent treatment with hydrazine.175... 

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