Lewis Acid-Promoted Cascade Reactions of Cyclopropenes: A Unified Approach to Stereoselective Synthesis of Cyclic Ethers and Oxaspirolactones

Abstract

Lewis acid promoted 5/6-exo trig hydroalkoxylation/reduction cascade of ω-hydroxy cyclopropenes gave eLewis acid promoted 5/6-exo trig hydroalkoxylation/reduction cascade of -hydroxy cyclopropenes gave expeditious, stereoselective access to THF/THP derivatives. Monoester substituted -hydroxy cyclopropenes on treatment with catalytic Bi(OTf)3 lead to [5,5]/[6,5] oxaspirocyclic lactones. This unified strategy relies on generation of transient donor-acceptor (D-A) cyclopropanes from -hydroxy cyclopropene precursors. This approach allows for the sequential addition of two nucleophiles in ‘one pot’ process for the synthesis of THP derivatives. The utility of this methodology is demonstrated in the stereoselective synthesis of homologue of (±)-civet.