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Polymer‐Supported Chiral Schrock Catalysts Immobilized via the Arylimido Ligand
Author(s) -
Wang Dongren,
Kröll Roswitha,
Mayr Monika,
Wurst Klaus,
Buchmeiser Michael R.
Publication year - 2006
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200606030
Subject(s) - chemistry , catalysis , ligand (biochemistry) , medicinal chemistry , stereochemistry , organic chemistry , biochemistry , receptor
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‐R 2 ‐anilines, i.e., {4‐[6‐X‐(CH 2 ) 6 ]‐2,6‐R 2 ‐C 6 H 2 ‐NH 2 } ( 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‐R 2 ‐4‐[6‐X‐(CH 2 ) 6 ]‐C 6 H 2 } 2 Cl 2 ⋅DME ( 11 : R=Me, X=Br; 12 : R=Me, X=Cl; 13 : R=2‐Pr, X=Cl; 14 : R=2‐Pr, X=Br). Compounds 11 – 14 were transformed into the corresponding Mo‐bis(imido)dialkyl complexes Mo{N‐2,6‐R 2 ‐4‐[6‐X‐(CH 2 ) 6 ]‐C 6 H 2 } 2 (CH 2 CMe 2 Ph) 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‐R 2 ‐4‐[6‐X‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)(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‐Me 2 ‐4‐[6‐Br‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[OC(CH 3 )(CF 3 ) 2 ] 2 ( 22 ) and Mo{N‐2,6‐(2‐Pr) 2 ‐4‐[6‐Cl‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[OC(CH 3 )(CF 3 ) 2 ] (23 ), Mo{N‐2,6‐Me 2 ‐4‐[6‐Br‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[( R )‐BIPHEN] ( 24 ) and Mo{N‐2,6‐(2‐Pr) 2 ‐4‐[6‐Br‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[( 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‐Me 2 ‐4‐[PS‐CH 2 ‐O‐CF 2 ‐CF(CF 3 )‐SO 3 ‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[OCMe(CF 3 ) 2 ] 2 ( 26 ), Mo{N‐2,6‐Me 2 ‐4‐[PS‐DVB‐CH 2 ‐O‐CF 2 ‐CF(CF 3 )‐SO 3 ‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[( R )‐BIPHEN] ( 27 ) Mo{N‐2,6‐(2‐Pr) 2 ‐4‐[PS‐DVB‐CH 2 ‐O‐CF 2 ‐CF(CF 3 )‐SO 3 ‐(CH 2 ) 6 ]‐C 6 H 2 }(CHCMe 2 Ph)[( 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.