Five-membered phosphacycles

In addition to direct DuPhos and BPE analogues, several other ligands containing five-membered phosphacycles have been reported (Fig. 24.6). As early as 1991, non-C2-symme trie phospholane-containing phosphines 37-39 were reported by Brunner and Limmer [7]. These were prepared by base-induced addition of the secondary phospholane to the appropriate diphenylphosphino-substi-tuted olefin. As for the symmetrical 3,4-disubstituted bisphospholanes, enantios-electivities for the Rh-catalyzed reduction of a-acetamidocinnamate were poor. 

Fig. 24.6 Alternative ligands containing five-membered phosphacycles.

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