Thioether macrocyclic complexes palladium

Finally, some work on macrocyclic thioethers was able to show that while a metal-free tetraester of a functionalised [14]aneS4 diol was non-mesomorphic as either its cis or trans isomer, complexation to palladium(II) stiffened the whole molecular unit and allowed differentiation between the non-mesomorphic, nonlinear cis complex ((312) y = l Cr 258 I), and the mesomorphic, linear trans complex ((312) y = 1 Cr 312 (N 272) Substituted with shorter lateral arms, the palladium salts (Pd(Bp4)2) exhibited monotropic SmC phases ((312) y = 0 Cr 222 (SmC 164) I). Difunctionalized tru 5-[16]aneS4 diol palladium ((313) MX = Pd(BF4)i, y = 0,l) also exhibited monotropic phase (SmC and N, respectively for y = 0 and 1), whereas the copper derivative ((313) y = 0, MX = Cu(PF6)) was surprisingly devoid of mesomorphism. Note that some related aza macrocyclic metal complexes as potential metallomesc ens were also studied, but it appeared that none of them were found to be mesomorphic. ... 

In addition to the success just described with the well-known named processes, a number of other macrocyclization reactions mediated by palladium complexes have been reported. The first of these approaches exploits the established chemistry of palladium Jt-allyl complexes for use in activation towards reaction with nucleophiles. This reaction was employed by Harran et al. as a critical step in the construction of a series of macrocycles such as 116 via 115) designed to significantly reduce the peptidic character of known active peptides (Scheme 11.14). " The approach tolerates a variety of functionality, including alcohols, amides, thioethers and selected heteroaromatics, and was also successfully conducted on solid support. 

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