Calixarene phosphites

SCHEME 4.19 The structures of the calixarenes phosphite 30,31. (Adapted from Ref. [78,79] with permission of Wiley-VCH and Royal Society of Chemistry.)... 

Calixarene phosphite 30 with unsubstituted hydroxyl group was used as a ligand in the rhodium complex-catalyzed hydroformylation of 1-hexene (Scheme 4.19) [78]. The almost quantitative conversion of initial alkene was observed in 3 hours with aldehyde yields of 80-85%. Unfortunately, the selectivity was low because the aldehydes with normal and isomerized chains were formed in similar amounts. A number of structurally similar phosphites 31 as components of catalytic systems for the hydroformylation of 1-octene are described (Scheme 4.19) [79], It was shown that the nature and steric volume of R did not significantly affect main processes. Thus, the depth of conversion was 80-90% with about 60% selectivity in all cases. 

The smaller p -tert-butyl-calix [4] arenes have a rich coordination chemistry as well (65). Of these, however, only the upper-rim modified calixarenes seem to support metal complexes with confined binding sites (66), except in those cases where the lower-rim substituents form an appended cavity. Thus, Matt and coworkers have reported (67) a pocket-shaped calix[4]arene ligand L2 bearing two lower-rim [([Pg.410]

Diethyl phosphate esters of the sterically congested phenols of calixarenes have been prepared in acceptable yields (>55%) and used in the preparation of meta-cyclophanes [8]. The corresponding reaction using diethyl phosphite, with triethylamine in place of the quaternary ammonium catalyst, results in only partial phosphorylation of the hydroxyl groups. 

Miscellaneous Reactions. Wittig technology has been used to prepare ylide-, phosphate-, phosphite- and phosphinate-terminated dendrimers, and calixarenes bearing pyridyl podands on their upper rim 7°... 

In nonpolar media, complexes with calixarenes modified with phosphine and phosphite groups have been used in hydroformylation [219,220]. Bagatin et al. [221] and Fang et al. [222] described the successful use of the diphenylphos-phinated calixarenes 80-81 in hydroformylation of styrene and 1-octene. 

A phosphite-modified calixarene with unsubstituted hydroxyl groups was used as a ligand in 1-hexene hydroformylation catalyzed by rhodium complexes [224], The reaction was carried out at a synthesis gas pressure of 6.0 MPa and 160 °C. Rh(acac)(CO)2 was a catalyst precursor. In 3 h, the conversion of the initial alkene virtually reached its theoretically predicted value the yield of aldehydes was 80-85%, and the normal-to-isomeric aldehyde ratio was approximately 1 1. Some similar phosphites 83 were also studied as components of catalytic systems for 1-octene hydroformylation [225]. It was shown that the nature and steric volume of substituent R have no essential effect on the main laws of the process. For example, the conversion was 80-90% at a selectivity with respect to nonanal of about 60% in all cases. The regioselectivity with respect to nonanal was considerably increased to 90-92% by using the chelate biphosphite 84 [220]. 

---