Construction of Phosphorus and Sulfur Stereogenic Centers by Chiral Cyclopentadienyl Rhodium(III) Catalysis
Phosphorus- and sulfur-stereogenic compounds are widely used as ligands in asymmetric transition-metal catalysis and as organocatalysts. These molecules also show a large potential for pharmaceutical and agricultural use. However, synthesizing them in a stereoselective manner remains a challenge. In the present thesis, a chiral cyclopentadienyl RhIII-catalyzed enantioselective CâH activation is described that gives access to P- and S-stereogenic compounds. A range of enantioenriched P-chiral heterocycles was accessed via desymmetrization of diaryl phosphinamides with internal alkynes. In addition, racemic chiral phosphinamides were kinetically resolved, yielding both the cyclic phosphinamide products and the unreacted acyclic phosphinamides with selectivity factors of up to 50. Prochiral sulfoximines were trapped with diazo compounds to give access to the corresponding enantioenriched 1,2-benzothiazine derivatives, with only water and nitrogen as side products. For the development of these methods, novel trisubstituted chiral CpX ligands and their rhodium complexes which exhibit superior reactivity and selectivity were prepared.