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C 2 ‐Symmetric 4,4′,5,5′‐Tetrahydrobi(oxazoles) and 4,4′,5,5′‐Tetrahydro‐2,2′‐methylenebis[oxazoles] as Chiral Ligands for Enantioselective Catalysis Preliminary Communication
Author(s) -
Müller Dieter,
Umbricht Gisela,
Weber Beat,
Pfaltz Andreas
Publication year - 1991
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.19910740123
Subject(s) - chemistry , enantioselective synthesis , oxazole , allylic rearrangement , catalysis , medicinal chemistry , diazo , nucleophile , cyclopropane , combinatorial chemistry , stereochemistry , organic chemistry , ring (chemistry)
The synthesis of a series of enantiomerically pure, C 2 ‐symmetric 4,4′,5,5′‐tetrahydro‐2,2′‐methylenebis[oxazoles] and 4,4′,5,5′‐tetrahydro‐2,2′‐bi(oxazoles) is reported. Copper complexes with anionic tetrahydromethylenebis[oxazole] ligands are efficient catalysts for the enantioselective cyclopropane formation from olefins and diazo compounds (up to 96% ee in the reaction of styrene with menthyl diazoacetate). Tetrahydrobi(oxazole)iridium(I) complexes were found to catalyze transfer hydrogenations of aryl alkyl ketones with i‐PrOH (up to 91% ee). Tetrahydrobi(oxazole)palladium complexes can be used as enantioselective catalysts for allylic nucleophilic substitution (up to 77% ee in the reaction of PhCHCHCH(OAc)Ph with NaHC(COOMe) 2 ).