ChemInform Abstract: 3‐Methoxypyrazoles from 1,1‐Dimethoxyethene, Few Original Results.

abstract From the condensation between 1,1-dimethoxyethene and anhydrides, synthetically useful b , b edimethoxye a , b -unsaturated ketones were prepared. Upon addition of hydrazine, followed by io-dination, 4-iodinated 3-methoxypyrazoles were obtained. The occurrence of a side compound alsoprovided insights in the scope of this synthesis. In a second part,1-(4-chlorophenyl)-3,3-dimethoxyprop-2-en-1-one was obtained from 1,1-dimethoxyethene and 4-chlorobenzoylchloride. The subsequent ad-dition of hydrazine or phenylhydrazine led to 5-(4-chlorophenyl)-3-methoxy-1H-pyrazole or 1-phenyl-5-(4-chlorophenyl)-3-methoxypyrazole in unprecedented 64 or 54% overallyield. Unexpectedly, additionof 2-pyridylhydrazine led to the 2-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-1-(4-chlorophenyl) ethanone. Thisled us to design original conditions, which led to the target 1-(2-pyridyl)-5-(4-chlorophenyl)-3-methoxypyrazole in a 39% overall yield. Additional examples are provided, starting from variouscarboxychlorides. 2012 Elsevier Ltd. All rights reserved.