Polymer-Supported Chiral Schrock Catalysts Immobilized via the Arylimido Ligand

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Abstract

The immobilization of both chiral and non-chiral versions of the Schrock catalyst via the arylimido ligand was accomplished for the first time. For this purpose, four different 4-(6-halogenohexyl)-2,6-R2-anilines, i.e., {4-[6-X-(CH2)6]-2,6-R2-C6H2-NH2} (7: R=Me, X=Br; 8: R=Me, X=Cl, 9: R=2-Pr, X=Cl, 10: R=2-Pr, X=Br) were prepared and used for the synthesis of the corresponding Mo-bis(imido)dichloro complexes Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}2Cl2⋅DME (11: R=Me, X=Br; 12: R=Me, X=Cl; 13: R=2-Pr, X=Cl; 14: R=2-Pr, X=Br). Compounds 1114 were transformed into the corresponding Mo-bis(imido)dialkyl complexes Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}2(CH2CMe2Ph)2 (15: R=Me, X=Br; 16: R=Me, X=Cl, 17: R=2-Pr, X=Cl; 18: R=2-Pr, X=Br). These were used for the synthesis of the Mo-imidoalkylidene triflates Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}(CHCMe2Ph)(OTf)2⋅DME (19: R=Me, X=Br; 20: R=2-Pr, X=Br, 21: R=2-Pr, X=Cl). Compounds 19--21 were used in the synthesis of the Schrock type catalysts Mo{N-2,6-Me2-4-[6-Br-(CH2)6]-C6H2}(CHCMe2Ph)[OC(CH3)(CF3)2]2 (22) and Mo{N-2,6-(2-Pr)2-4-[6-Cl-(CH2)6]-C6H2}(CHCMe2Ph)[OC(CH3)(CF3)2] (23), Mo{N-2,6-Me2-4-[6-Br-(CH2)6]-C6H2}(CHCMe2Ph)[(R)-BIPHEN] (24) and Mo{N-2,6-(2-Pr)2-4-[6-Br-(CH2)6]-C6H2}(CHCMe2Ph)[(R)-BIPHEN] (25). Compounds 22, 24 and 25 were immobilized on Ag-perfluoroalkylsulfonate-modified PS- and PS-DVB materials to yield the corresponding immobilized catalysts Mo{N-2,6-Me2-4-[PS-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}(CHCMe2Ph)[OCMe(CF3)2]2 (26), Mo{N-2,6-Me2-4-[PS-DVB-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}(CHCMe2Ph)[(R)-BIPHEN] (27) Mo{N-2,6-(2-Pr)2-4-[PS-DVB-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}(CHCMe2Ph)[(R)-BIPHEN] (28). These were used in a series of ring-closing metathesis (RCM), ring-opening cross metathesis, asymmetric RCM and desymmetrization reactions. The use of 27 and 28 resulted in values for enantiomeric excess (ee) virtually identical to those obtained with the corresponding homogeneous chiral catalysts.

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