25016-18-6Relevant academic research and scientific papers
3-Methoxypyrazoles from 1,1-dimethoxyethene, few original results
Salanouve, Elise,Guillou, Sandrine,Bizouarne, Marine,Bonhomme, Frédéric J.,Janin, Yves L.
experimental part, p. 3165 - 3171 (2012/06/01)
From the condensation between 1,1-dimethoxyethene and anhydrides, synthetically useful β,β-dimethoxy-α,β-unsaturated ketones were prepared. Upon addition of hydrazine, followed by iodination, 4-iodinated 3-methoxypyrazoles were obtained. The occurrence of a side compound also provided 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 addition 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% overall yield. Unexpectedly, addition of 2-pyridylhydrazine led to the 2-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-1-(4-chlorophenyl) ethanone. This led 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 various carboxychlorides.
MIGRATION TENDENCIES OF FUNCTIONAL GROUPS TOWARD SIGMATROPIC REARRANGEMENT IN 3,3-DISUBSTITUTED 3H-PYRAZOLES
Schiess, Peter,Stalder, Henri
, p. 1417 - 1420 (2007/10/02)
3,3-Disubstituted 3H-pyrazoles la - e aromatise through an intramolecular sigmatropic 1,5-(1,2-)shift of one of the quaternary groups.From a kinetic study of the uncatalysed and of the acid catalysed isomerisation reaction migration tendencies of functional groups in sigmatropic rearrangement toward neutral and toward cationic centers are obtained.
