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On the Origin of Asymmetric Induction of the Palladium‐Catalyzed Allylic Substitution Reaction with Chiral 4,4‐Disubstituted 4,5‐Dihydro‐2‐(phosphinoaryl)oxazole Ligands
Author(s) -
Schaffner Silvia,
Müller Jürgen F. K.,
Neuburger Markus,
Zehnder Margareta
Publication year - 1998
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19980810533
Subject(s) - chemistry , oxazole , palladium , allylic rearrangement , ligand (biochemistry) , substitution reaction , asymmetric induction , stereochemistry , tsuji–trost reaction , catalysis , medicinal chemistry , substitution (logic) , enantioselective synthesis , organic chemistry , biochemistry , receptor , computer science , programming language
The X‐ray analyses of (η 3 ‐allyl){4‐benzyl‐2‐[2‐(diphenylphosphino‐κP)phenyl]‐4,5‐dihydro‐4‐4‐methyloxazole‐κ N }palladium(II) hexafluorophosphate ( 5 ) and the analogous [Pd(η 3 ‐1,3‐diphenylallyl)] complex 6 are presented. A comparison with the (η 3 ‐allyl)‐ and (η‐1,3‐diphenylallyl)palladium complexes 2 and 3 , respectively, containing the 4‐monosubstituted 4,5‐dihydro‐2‐(phosphinoaryl)oxazole ligand 1a reveals important structural differences ( Fig. 3 ). 1 H‐NMR Spectroscopic investigation confirm that the 4,4‐disubstituted 4,5‐dihydro‐2‐(phosphinoaryl)oxazole ligand 4 of 5 and 6 shows the same conformation in solution as in the solid state ( Table 2 ). The application of ligand ( S )‐ 4 in the Pd‐catalyzed allylic substitution demonstrates a configurational relationship between the orientation of the allyl ligand in the intermediate ( cf. complex 6 ) and the absolute configuration of the allylic‐substitution product ( Table 3 ).