Asymmetric Multicomponent Propargylations via Carbon Dioxide Shuttling and Fixation

Catalytic asymmetric propargylic substitution reactions
have received
phenomenal progress and applications, but no study focuses on CO2 gas capture and fixation in this area. The released CO2 gas from the carbonate leaving group is usually taken as
a waste. Herein, we describe a feasible strategy for unexplored asymmetric
propargylation and alkynylallylic substitutions with CO2 shuttling and CO2 fixation. In addition, the Cu-catalyzed
asymmetric multicomponent propargylation is also established, through
which 13C-labeled CO2 is easily anchored into
enantioenriched skeletons. With these two protocols, a series of valuable
oxazolidinones, amino alcohols, and azetidine are prepared in high
yields and enantioselectivities and applied to the concise asymmetric
synthesis of natural product (−)-Cytoxazone. Extensive mechanistic
experiments suggest the favorable role of DABCO in CO2 capture
and the carboxylative cyclization as a potential rate-limiting process.