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1 2007

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Selective Nucleophilic Substitution Using Pyrazolate Anions: Easy Approach to Modular Chiral Ligands with Complexing Pyrazole Moieties

Kowalczyk R., Skarżewski J.

Polish Journal of Chemistry

2007

Vol. 81, nr 11

1987-1999

A simple method for the stereoselective synthesis of 3,5-disubstituted pyrazolyl alcohols from readily available chiral epoxides is reported. The key step of the synthesis is the ring-opening reation, which occurs by a regio- and enantioselective nucleophilic substitution with pyrazolate anions. An analogous reaction of the pyrazolate anions gave nonracemic (pyrazolyl)oxazolines. Thus obtained modular pyrazole chiral ligands were tested in the Pd-catalyzed Tsuji-Trost and Cu-catalyzed asymmetric cyclopropanation reactions and the enantioselectivities up to 52% ee and 64% ee were at tained in both model reactions, correspondingly.