Metal Template Synthesis and Coordination Chemistry of Functionalized P-Chiral Phosphanorbornenes

Abstract

The organopalladium complex containing the (S)-form of ortho-palladated (1-(dimethylamino)ethyl)-naphthylalene has been used successfully as the chiral template to promote the asymmetric cycloaddition reactions between coordinated 3,4-dimethyl-1-phenylphosphole and two dienophiles: N,N-dimethylacrylamide and styrene. The mechanism, the rate and the stereoselectivity of these chiral template promoted reactions are affected by the number of coordination sites available on the palladium template and the coordination potential of the dienophiles. At room temperature, the intramolecular cycloaddition reaction with N,N-dimethylacrylamide gave the corresponding P-chiral (−)-(Sp)-exo-amidophosphanorbornene stereospecifically in 3d. Under similar conditions, the corresponding intermolecular process gave a pair of separable diastereomeric endo-substituted amidophosphanorbornene complexes in 32d. With styrene, the intermolecular cycloaddition reaction at 80°C gave a pair of diastereomeric endo-substituted phenylphosphanorbornene complexes in 3d. No exo-cycloaddition reaction occurred when styrene was used as the dienophile. The first optically active and stable amido-O bonded platinum complex (Rp,Rp)-[Pt(exo-amidophosphanorbornene-P,O)2](ClO4)2 and its palladium analogue have been isolated and characterized by 31PNMR spectroscopy and X-ray crystallography.