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Stereoselective Synthesis of Spiro-2-oxabicyclo[2.2.2]octane Enabled by Ag(I)/ Brønsted Acid Relay Catalysis
- Zhang, Qingyu, Wang, Jianping, Wei, Yansheng, Zhai, Hongbin, Li, Yun
- Organic letters 2019 v.21 no.6 pp. 1694-1698
- Bronsted acids, alkynes, catalytic activity, chemical reactions, chemical structure, silver, stereoselective synthesis
- A highly stereoselective synthesis of a spiro-cineole scaffold that contains four stereogenic centers from readily accessible 2-alkynylbenzaldehydes and styrenes under very mild reaction conditions was reported. This cascade reaction involves a Ag(I)-catalyzed alkyne cycloisomerization and oxa-[4 + 2]-cycloaddition to give an oxonium intermediate which subsequently undergoes a previously unexplored 1,2-alkyl migration to access highly strained spiro-2-oxabicyclo[2.2.2]octanes in high yields with excellent stereoselectivities.