Thieme Chemistry Journal Awardees - Where Are They Now? Triflic Imide Catalyzed Cycloaddition Reactions

Abstract

This Account summarizes our recent development of triflic imide(Tf 2 NH)-catalyzed cycloaddition and cascade reactions. Reactionsof electron-rich olefins, possessing a silyl group, with α,β-unsaturatedcarbonyl compounds afforded highly substituted cyclobutanes, cyclopentanes,and bicyclo[4.2.0]octanes in good to excellentyields. In the reactions, Tf 2 NH acts as a precatalystto produce a strong Lewis acid, silyl triflic imide, which activatesthe cycloaddition reactions. Reactions of electron-rich olefinswith aldimines furnished highly substituted heterocycles such aspiperidines, quinolines, and pyrrolidines. In these cases, Tf 2 NHacts as a strong Bronsted acid. Moreover, it was foundthat Tf 2 NH can catalyze more than two mechanisticallydistinct reactions in one pot (tandem catalysis), so that a varietyof molecular skeletons can be constructed in a single operation. 1 Introduction 2 (2+2) Cycloaddition of α,β-UnsaturatedEsters 2.1 (2+2) Cycloadditon with Silyl Enol Ethers 2.2 (2+2) Cycloaddition with Allylsilanes 3 (3+2) Cycloaddition of Donor-Acceptor Cyclopropanes 4 Multicomponent Reaction: Cascade (4+2)-(2+2)Cycloaddition 5 Cycloaddition of Imines 5.1 Aza-(4+2) Cycloaddition with 2-Siloxydienes 5.2 Cascade Povarov-Hydrogen-Transfer Reaction withAllylsilanes 5.3 Aza-(3+2) Cycloaddition with α,α-Dimethylallylsilanes 6 Conclusions