Pyridinylpyrazole complexes

Analysis of palladium(II) pyridinylpyrazole complexes. Satake et al have reported the results of a study of the complexation of palladium(II) chloride with several pyridinylpyrazole analogues and their characterization in part through the use of long-range HMBC data. chemical shift data were reported for a number of... 

Table 34. N chemical shift assignments for a series of pyridinylpyrazole complexes with...

In several cases the nucleophilic attack on a n-allylpalladium complex 97 has been observed to occur on the central carbon atom of the allylic moiety. The resulting palladacy-clobutane derivative 98, instead of /3-hydride eliminadon, underwent reductive elimination furnishing a cyclopropane derivative 99. In spite of theoretical predictions which, appear to rule out such reactions, " they have been observed experimentally (Scheme 23). Thus, in the Pd-catalyzed reactions of cyclopropylideneethyl acetate 100 with ketene alkyl silyl acetals 101, the spiropentylacetates 103, albeit in low yield, along with the normal products 102 were observed.With Tj -allylpalladium-pyridinylpyrazole complexes 108 as catalysts this reaction mode of allyl acetates 104 with ketene acetals 105 became predominant so that cyclopropylacetates 106 were obtained as the main products (Scheme 23). An enantioselective version of this cyclopropane formation has also been reported. ... 

---