Tertiary phosphine ligands with nitrogen-containing substituents

2 TERTIARY PHOSPHINE LIGANDS WITH NITROGEN-CONTAINING SUBSTITUENTS 

The first amino-phosphines used in AOC for studies of catalyst recovery by aqueous extraction, 59, were prepared by radical addition of PH3 on dialkylallilamines [61]. Similar addition of diphenylphosphine on activated alkenes [33] resulted in formation of a variety of phosphines including also 66. 

Palladium catalyzed P-C cross coupling [58] between primary or secondary phosphines and appropriate aryl iodides made possible the preparation of several aminophenyl-phosphines with the general formula 70 and also the bisphosphine 71. 

Strongly basic cationic phosphine ligands 75, 76 containing guanidino functions were prepared either in the reaction of 3-aminopropyldiphenylphosphine with lH-pyrazole-l-carboxamide under basic conditions in DMF [75] or by the addition of dimethylcyanamide to the amino groups of tertiary (3-aminophenyl)phosphines in acidic medium [70], These phosphines (as acetate or chloride salts) are highly soluble in water in some cases the solubility reaches that of TPPMS. Another noteworthy feature of these compounds that they are considerably less sensitive to air oxidation then the anionic (e.g. sulfonated) phosphines. 

KP(C6H4-4-NMe2)2 reacts with the appropriate diol ditosylates yielding the chiral phosphines 77-79. These analogs of the well known Chiraphos, BDPP (Skewphos) and DIOP can be made water soluble by protonation or quatemization. Quatemization can be achieved with (CH3)3OBF4 with the phosphorus atoms protected by complexation to Rh(I) [76], This method of quatemization was originally introduced [77] to prepare 81 in its rhodium complex. It is remarkable, that DIOP which is known to be acid sensitive survives all these manipulations. 

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