DPPF ligand alkylphosphines

A-Arylhydrazones are useful agricultural materials. Moreover, they can be cleaved to form A-arylhydrazines for pyrazole synthesis, and the hydrazine portion can be transferred to ketones to serve as substrates for the Fischer indole synthesis.t The reactions of benzophenone hydrazone with aryl halides have been reported, and to date these reactions are best conducted with chelating phosphine ligands such as DPPF and BINAP, as shown in Eq. 22. These catalyst systans have been the only ones reported for hydra-zone arylation. The chemistry of hydrazonato complexes is similar to that of aniUdes and diarylamides.f Thus, the reactions of aryl chlorides with hydrazones should be accessible in the future using alkylphosphine ligands. 

Using NiCl2 without ligand resulted in development of efficient catalytic system for addition of alkylphosphinates not only to terminal, but also to internal alkynes (Scheme 8.38) [100]. For terminal alkynes a mixture of a and p isomers was obtained with different substituents. Addition reaction to alkenes was more difii-cult compared to the same reaction involving alkynes [100]. For example in reaction with 1-octene 100% yield was found with Pd catalyst, but only 25% with NiCli. In the presence of phosphine ligand the yield was increased to 69% (L = dppf). Some other reactions of phosphinates addition to the multiple bonds have been also studied [101-104]. 

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