Phosphites catechol-based

The use of catechol-based phosphites with PEG moieties in the thermoregulated phase-transfer hydroformylation of 1-decene was also investi-... 

Scheme 2 Synthesis of PEG-modified catechol-based phosphites...

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. 

As discussed for biphenol-based phosphites, phosphites derived from ClMeO-biphenol should also be sterically more demanding and have an increased ring size as compared to catechol-based phosphites. Moreover, by comparing the catalytic results of biphenol- and ClMeO-biphenol-based ligands, conclusions on the influence of the substitution pattern and resulting electronic effects on the activity and selectivity in the hydroformylation can be drawn. Therefore, ClMeO-biphenol-based phosphites with PEG side chains consisting of one to three ethylene glycol units were included in the present study. 

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-... 

Studies on the synthesis of cage-like phosphoranes based on casade reactions of trivalent phosphorus derivatives with unsaturated activated compounds has continued. For example, reactions of phosphites bearing dioxaphosphorinane (1), dioxaphospholane (2) and catechol derivatives (3) with hexafluoroacetone, chloral, mesoxalic and trifluoropyruvic acid esters have been performed to produce a series of novel carcass -type pentacoordinated phosphoranes with high regio- and stereoselectivity. Hence, upon treatment of hexafluoroacetone (4) with phosphites (1) and (2), pen-taoxophosphoranes (5) and (6) were formed (Scheme 1). 

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