Asymmetric Synthesis with Chiral Cyclic Phosphorus Auxiliaries

Abstract Phosphoryl-stabilized α-, β-, and γ-carbanions can be used in stereoselective alkylations, allylations, aminations and re­arrangements as well as in Michael addition and cyclopropanation reactions. Stoichiometric protocols are also used in asymmetric Wittig-Horner olefinations. The use of the P=O group as a Lewis base opens the path to catalytic carbonyl additions of various organometallic reagents. With trichlorosilylenolethers a new catalytic version of the aldoladdition has been invented. Phosphinamide borane­ complexes are the new brother of the famous CBS process for the asymmetric reduction of ketones. Epoxides can be ring-opened by SiCl 4 /P=O-Lewis base or as vinyl oxiranes with organocuprates, catalyzed by phosphoramidites. The latter method has found widespread use for the conjugate addition to α,β-unsaturated systems. Interesting enough, similar phosphites and phosphoramidites can also be used as ligands in hydrogenations and hydroformylations. Finally, the predecessors of many of these ligands have been introduced as chiral derivatizing and shift reagents. 1 Introduction 2 Stoichiometric Reactions 2.1 Phosphoryl-Stabilized Carbanions (P-V) 2.2 Horner-Wadsworth-Emmons Olefinations (P-V) 3 Catalytic Reactions 3.1 Nucleophilic Additions to Aldehydes (P-V) 3.2 Catalytic Aldol Additions (P-V) 3.3 Catalytic Ketone Reductions (P-V) 3.4 Catalytic Ring-Opening of Epoxides (P-V/P-III) 3.5 Catalytic Conjugate Additions (P-III) 3.6 Catalytic Hydrogenations and Hydroformylations (P-III) 4 Phosphorus Shift Reagents (P-V/P-III) 5 Miscellaneous 6 Conclusion and Outlook