Guanidinium phosphines

The guanidinium phosphine 1 (cf. Fig. 2) was also successfully tested for allylic substitutions. The reaction of allyl acetate 6 and malonate 7 afforded coupling product 8 in 56% yield. The palladium leaching was determined to be about 0.3% (Scheme 5). 

Water-soluble phosphine ligands containing m-guanidinium moieties were synthesized and applied to aqueous Heck coupling reactions.149 High temperature appears beneficial for Heck-type coupling of simple alkenes in water.150... 

At the same time, Schmidtchen et al. compared cationic phosphine ligands containing the hydrophilic guanidinium (4.3, 4.4) and the anionic phosphine ligand TPPTS for this palladium-catalyzed coupling reaction. They found that the cationic ligands were effective for the coupling reaction but less efficient than TPPTS 43... 

DMSO, dimethyl sulphoxide bipy, 2,2,-bipyridyl TPPO, triphenyl phosphine oxide GD, guanidinium DPAE, l,2-di(pyridine-2-aldimino)ethane EPAE, ethylenediaminetetraacetate. 

Guanidinium-modified diphosphine ligands modified with a xanthene backbone or quaternized imidazolium-substituted phosphines with associated [Rh(acac)(GO)2] show high overall catalytic activity and high regioselectivity in the biphasic hydroformylation of oct-l-ene using hexafluorophosphate imidazolium Similarly, a wide... 

In the context of the phospha-Mannich reaction, secondary phosphine oxides were added on the C = N bond of imines in the presence of chiral guanidinium salt catalysts to give the a-aminophosphine oxides in an enantioselective way (Scheme 29). " ... 

A novel guanidinium catalyst (602), obtained in a single step from a commercially available diphenylethylenediamine, has been prepared by Tan and co-workers ° and used in the synthesis of a series of enantiomerically enriched a-amino phosphinates (601) from /f-phosphinates (599) containing a P-chiral center and A-tosylimines (600) (Scheme 149). 

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