Journal of the American Chemical Society, Vol.138, No.12, 3994-3997, 2016
Intermolecular Homopropargyl Alcohol Addition to Alkyne and a Sequential 1,6-Enyne Cycloisomerization with Triazole-Gold Catalyst
While gold-catalyzed homopropargyl alcohol cyclization is a known process, a triazole-gold catalyst prevented the intramolecular cyclization in the presence of terminal alkynes. As a result, an intermolecular addition to ail alkyne was achieved. A sequential 1,6-enyne cycloisomerization gave the unusual 2,3-dihydrooxepine, which revealed another new reaction path. Diels-Alder reaction of oxepine followed by a 1,3-alkoxyl shift gave hydrobezofuran derivatives in high yields. Diasterioselective reaction of homopropargyl alcohol to final product enabled one-step formation of five stereogenic centers with excellent enantiomeric selectivity.