50473-61-5Relevant articles and documents
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.
Addition of silyloxydienes to 2,6-dibromo-1,4-benzoquinone: An approach to highly oxygenated bromonaphthoquinones for the synthesis of thysanone
Barker, David,Brimble, Margaret A.,Do, Peter,Turner, Peter
, p. 2441 - 2449 (2007/10/03)
The synthesis of tetraoxygenated bromonaphthoquinones 6a, 6b, 6c, 6d, key intermediates for a synthesis of the 3C protease inhibitor, thysanone, were investigated. Addition of 1-methoxy-1,3-bis(trimethylsilyloxy)-1,3-butadiene 8 to 2,6-dibromo-1,4-benzoquinone 10 in benzene afforded a mixture of naphthoquinone 6a, arising from Diels-Alder addition followed by aromatisation, and Michael adduct 12. The Michael adduct 12 predominated when THF was used as solvent whereas 6a predominated when benzene was used. Naphthoquinone 6a underwent benzylation to naphthoquinone 6c. Addition of 1,1-dimethoxy-3-trimethylsilyloxy-1,3-butadiene 9 to 2,6-dibromo-1,4-benzoquinone 10 followed by benzylation failed to afford the desired bromonaphthoquinone 6d yet methylation did afford naphthoquinone 6b. Bromonaphthoquinone 6d was finally prepared from naphthol 18, obtained from addition of diene 9 to 1,4-benzoquinone 17, followed by ortho-bromination and oxidation. Attempted Sakurai allylation of bromonaphthoquinone 6d afforded naphthodihydrofuran 21. A similar observation was observed for 2-carbomethoxy-1,4-naphthoquinone 22 that also underwent Sakurai allylation to afford naphthodihydrofuran 23. The structure of Michael adduct 12 was confirmed by X-ray crystallography.
