BINAP ligand hydrazones

Directed and Asymmetric Reduction The principles of directed and asymmetric reactions were first developed for hydrogenation, as discussed in Section 9.2. Asymmetric hydrosilation of ketones can now be carried out cata-lytically with rhodium complexes of diop (9.22). The new chiral ligand Et-duPHOS, made by Burk at du Pont, allows chiral amination of ketones via Eq. 14.50. Note how the use of the hydrazone generates an amide carbonyl to act as a ligand, as is known to favor high e.e. (see Section 9.2). Noyori s powerful BINAP ligand has been applied to a large number of asymmetric reactions. 

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. 

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