176300-50-8Relevant articles and documents
Evidence for the in situ formation of copper acetylides during Pd/Cu catalyzed synthesis of enynes: A new synthesis of allenynols
Bertus, Philippe,Fecourt, Fabien,Bauder, Claude,Pale, Patrick
, p. 12 - 14 (2004)
The in situ formation of copper acetylide in Pd/Cu catalyzed coupling reactions of acetylenic derivatives has been demonstrated by the reaction with ethynyloxiranes, which provides allenynols; a new Cu catalyzed route to the latter has also been found.
6-Endo- and 5-exo-digonal cyclizations of o-hydroxyphenyl ethynyl ketones: A key step for highly selective benzopyranone formation
Nakatani, Kazuhiko,Okamoto, Akimitsu,Saito, Isao
, p. 9427 - 9446 (2007/10/03)
The cyclization of o-hydroxyphenyl ethynyl ketones was examined from theoretical and experimental standpoints in order to develop efficient synthetic methods for the construction of 2-substituted pyranones possessing significant biological activities. Ab initio studies at HF/6-31G* level on the cyclization indicated that both 6-endo-digonal and 5-exo-digonal cyclizations giving benzopyranones and benzofuranones, respectively, were endothermic and reversible in aprotic media, and the irreversible protonation of the resulting unions would be critical for the products formation. We generated phenoxide ion under aprotic conditions in situ by desilylation of o-silyloxyphenyl ethynyl ketones with spray dried potassium fluoride and 18- crown-6 in anhydrous DMF. Under these conditions the cyclization of variety o-hydroxyphenyl ethynyl ketones proceeded smoothly to produce benzopyranone derivatives with exceedingly high selectivity. Theoretical and experimental results strongly suggested that the presence of a small amount of proton donor effecting the protonation of the resulting benzopyranone union was essential for the high 6-endo-diagonal selectivity.
