Progress on the Enantioselective Synthesis of Axially Chiral Cycloalkylidenes

Abstract The discovery of new asymmetric synthetic methodologies and the asymmetric synthesis of new chiral compounds have been a major focus of synthetic organic chemists for decades. Axially chiral compounds have gained considerable attention in recent years because of their widespread utility in asymmetric catalysis and synthesis. Methods for the asymmetric synthesis of axially chiral cycloalkylidenes, a subset of axially chiral molecules, are far fewer compared to those developed for the preparation of chiral allenes and chiral biaryl compounds. In this review, different approaches for the synthesis of axially chiral cycloalkylidenes are summarized. 1 Introduction 2 Methods for the Enantioselective Synthesis of Axially Chiral Cycloalkylidenes 2.1 Asymmetric Synthesis of Axially Chiral Cycloalkylidenes 2.1.1 Asymmetric Horner–Wadsworth–Emmons (HWE) Reactions 2.1.2 Asymmetric Wittig Reactions 2.1.3 Asymmetric Dehydrohalogenation Reactions 2.1.4 Asymmetric Elimination Reactions of Chiral Sulfoxides/Selenoxides 2.1.5 Kinetic Resolution of Prochiral Compounds 2.1.6 Other Miscellaneous Methods 2.2 Catalytic Asymmetric Synthesis of Axially Chiral Cycloalkylidenes 3 Conclusion