Novel conversions and coupling reactions of chalcones and their epoxides
- 1 January 1977
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 1
- No. 2,p. 134-138
- https://doi.org/10.1039/p19770000134
Abstract
Chalcones undergo photoisomerization from trans- to the hitherto unknown cis-forms only when available phenolic hydroxy-functions are fully substituted. The cis-chalcones ere metastable and revert immediately to trans-isomers during acidic hydrolysis of protective acetal groups. Both trans- and cis-isomers of fully O-substituted chalcones form stable trans-epoxides with alkaline hydrogen peroxide. These can serve as-synthetic intermediates, as in the synthesis of a pair of 2-hydroxy-3-methoxy-3-phenylpropiophenone racemates by acidic hydrolysis in methanol (SN1 mechanism) and of α-hydroxychalcones (alkaline hydrolysis). Stereoselective β-addition of phenolic nuclei via unstable epoxide intermediates (SN2 mechanism) occurs with alkaline peroxide when a 4-hydroxy-function is present in the chalcone, giving structural isomers of 3,3-diaryl-2-hydroxypropiophenones.Keywords
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