Atropisomeric Biarylbisphosphines Derived from 2,2-Difluoro-1,3-benzo­dioxole

Abstract

Starting from the inexpensive 2,2-difluoro-1,3-benzodioxole or its 5-bromo derivative, two new atropisomeric bisphosphines have been prepared which, after racemate resolution, exhibit attractive features as ligands for enantioselective catalysts. The key step in their synthesis is a low temperature Ullmann reaction. An improved protocol secures coupling yields of 70-80%.

Key words

atropisomers - 2,2-difluoro-1,3-benzodioxole - bromo/lithium permutation - metalation - biarylbisphosphines

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18

Michel, D.; Lonza AG, Visp, unpublished results, 2002.

20

Mettler, H. P.; Haesakkers, P.; Lonza AG, Visp, unpublished results, 2002/2003.