Phosphites, biphenol backbone

The catechol-based hgands 14 show fairly low selectivity similar to that of the unmodified system. In contrast, the biphenol-derived phosphites 17 gave excellent chemoselectivity. The best results were obtained with 17c, where a TOP of ca. 1900 h was achieved which is close to the maximum value of 2000 h The n-selectivity of 71% was also appreciable, corresponding to an n/iso ratio of 2.4. The substituents in the biphenol backbones in hgands 19 re-... 

A second set of ligands was prepared on the basis of biphenol as backbone for the cyclic structure. This results in a seven-membered rather than a five-membered ring as compared to the catechol-based phosphites, furthermore, the biphenol derivatives can be expected to be sterically more demanding than catechol ligands. 

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