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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Catalytic (2 + 2)-cycloaddition reactions of silyl enol ethers. A convenient and stereoselective method for
Kiyosei Takasu1, Megumi Ueno, Kazato Inanaga
1Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan.
Abstract:
An efficient catalytic (2 + 2)-cycloaddition reaction leading to the formation of cyclobutane rings has been devised. The process transforms silyl enol ethers and alpha,beta-unsaturated esters into polysubstituted cyclobutanes with a high degree of trans-stereoselectivity. Both the rate and stereoselectivity of the process can be controlled by the choice of the ester group and silyl substituents. The results of stereochemical studies show that the cycloaddition step in this reaction proceeds in a nonstereospecific manner and, thus, by a pathway involving sequential nucleophilic additions via a short-lived zwitterionic intermediate.
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