Phosphinic amides reduction

The JV-silyl phosphinous amides present some particularities in their reactivity that make these compounds worth commenting on separately. They are stable and can be easily prepared in the usual way by reaction of AT-silyl substituted primary amines or hexamethyldisilazane with halophosphanes [48,49,128,129] or byJV-silylation of the appropriate phosphinous amides [72, 107]. The reductive Ph-P bond cleavage in AT-silyl phosphazenes Ph3P=NSiMe3 by the action of sodium is a peculiar example of preparing Ph2PNHSiMe3 [130]. 

Reduction of amides is an important preparative method for the synthesis of primary amines. Reducing agents used for this purpose include lithium aluminum hydride, sodium borohydride, triphenyl-phosphine (Staudinger reduction), and thiols. In the present case it is important to consider the compatibility of the reduction system with the carboxylic and methanesulfonic acid functions. Platinum and palladium arc often used for catalytic reduction. 

As for the reduction of the ketones, the amphoteric catalysts featuring acidic-basic sites have been found to be very effective for the enantioselective catalysis of C-C bond formation. Thus, Soai et al. were the first to report the enantioselective addition of dialkylzincs to aldehydes using enantiomerically pure phosphin-amides and analogues as chiral catalysts in the presence of titanium tetraiso-propoxide. Numerous chiral organophosphorus compounds have been prepared and applied in a test reaction between benzaldehyde and diethylzinc [48, 49]. An important difference in terms of enantioselectivity was observed between the behavior of P=S (47-48) and P=0 (49) groups. Thus, the enan-... 

The carbonylation of aryl halides with alcohols and amines catalysed by palladium complexes with triphenylphosphine ligand is the convergent and direct route to the synthesis of aromatic esters as well as aromatic amides. Even though these palladium complexes are widely employed as the best catalytic system, those catalysts are difficult to separate and reuse for the reaction without further processing. The major drawbacks are oxidation of triphenylphosphine to phosphine oxide, reduction of palladium complex to metal and termination of the catalytic cycle. The phosphine-free, thermally stable and air resistant catalyst (1) containing a carbon-palladium covalent bond (Figure 12.3) has been found to be a highly selective and efficient catalyst for the carbonylation of aryl iodides.[1]... 

The oxime from (4-chloro-l-oxobutyl)phosphonic acid has been cyclized to Pro ". An unusual rearrangement based on valence expansion of phosphorus is of interest the treatment of an (oxoalkyl)phosphonic oxime with Ph2PCl initially yields the phosphorus(III) derivative, but this rearranges spontaneously to give a phosphinic amide derivative 300, reduction of which then affords the [(V-diphenylphosphinoylamino)alkyl]phosphonic acid, readily hydrolysable under acid conditions to the free (aminoalkyl)phosphonic diester (Scheme 34)" ". 

The bisphosphonate - upon reduction with lithiumaluminum hydride in ether at 0°C - produced the amide functionalized primary bisphosphine (1) in good yields [45]. This reaction proceeded to reduce the amide group in 1 to produce the amine functionaUzed primary bisphosphine (2) in <5% yields. The amido bisprimary phosphine 1 is an air stable crystalline solid whereas the amine compound 2 is an oxidatively stable liquid. Separation of 1 and 2 in pure forms was achieved using coliunn chromatography. The amidic bisprimary phosphine 1 was crystallized from chloroform and exhibits remarkable stability not only in the solid state but also in solution as well. The crystal structure of the air stable primary his-phosphine 1 as shown in Fig. 1 is unprecedented to date. 

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