Brønsted Base‐Catalyzed Tandem Isomerization–Michael Reactions of Alkynes:
- TCHLab
- Dec 3, 2010
- 1 min read
Synthesis of Oxacycles and Azacycles
Hongjun Liu, Wei Feng, Choon Wee Kee, Dasheng Leow, Wei‐Tian Loh and Choon‐Hong Tan
Advanced Synthesis and Catalysis, 2010, 352, 3373 – 3379.
Abstract: An efficient synthesis of oxacycles and azacycles was developed using a Brønsted base‐catalyzed tandem alkyne isomerization–Michael reaction sequence. Functionalized 2‐alkylidenetetrahydrofurans were prepared by an intramolecular oxy‐Michael reaction on an allene that was generated in situ from an alkynoate. The aza‐Michael version using alkynylamines, alkynylamides and alkynyl carbamates led to piperidines, lactams and oxazolidinones, respectively. An enantioselective version of this reaction resulted in an axially chiral lactam with high enantioselectivity. Some alkynes, however, were unable to complete the intramolecular Michael reactions and provided enantioenriched allenes.
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