Reaction of 2‐acyl‐3‐aminobenzofurans with hydrazines

While 2‐acetyl and 2‐benzoyl‐3‐aminobenzofurans did not react with hydrazine, monomethyl‐ and N,N ‐dimethylhydrazine to give the related hydrazones, their 3‐ N ‐( p ‐toluenesulfonyl) derivatives afforded them smoothly in good yields. Depending upon reaction conditions, products arising from hydrazone cyclization to benzofuropyrazoles and/or from furan ring cleavage at the C2O bond to give 5‐(2‐hydroxyphenyl)pyrazoles were also formed. The formation of these products depends upon hydrazones configuration and is discussed. Only ( E )‐isomers appear to undergo furan ring opening. In acidic media at room temprature either the hydrazones or the monomethylhydrazones gave the same related α‐azines. Microanalyses, ir, uv, 1 H‐nmr and ms spectra are in agreement with the proposed structures.