61844-17-5Relevant academic research and scientific papers
ON THE MECHANISM OF THE 1-BENZOXEPIN RING FORMING REACTION BY SULPHUR YLIDE ANNULATION OF 2-(o-HYDROXYPHENYL) ALKYL KETONES
Arnone, Alberto,Bravo, Pierfrancesco,Ticozzi, Calimero
, p. 195 - 200 (2007/10/02)
The course of the reactions between ortho-hydroxybenzylacetone, 1a, and -acetophenone, 1b, and dimethylsulphoxonium methylide, 2, in DMSO-d6 has been followed by high-field 1H NMR spectroscopy.It has been demonstrated that both reactions proceed via the formation of epoxide intermediates 5a,b then undergoing opening of the epoxide ring with intramolecular nucleophilic displacement by the phenolic group to afford, directly in the reaction medium, 3-hydroxy-2,3,4,5-tetrahydro-1-benzoxepins 6a,b and 3,4-dihydro-2-hydroxymethyl-2H-1-benzopyrans 7a,b in a ratio of ca. 4:1 and 6:1, respectively.By contrast, it has been proved that, by quenching the DMSO-d6 reaction mixtures with an aqueous acidic medium or with an aqueous basic medium, 5a,b afforded the chroman derivatives 7a,b preferentially.The possibility of converting products 6 and 7 into one another or into the open-chain epoxide 5 has also been studied.
