Phosphine oxides aminophosphine

The hydrolysis of tervalent phosphorus acid derivatives with two P—C bonds leads to secondary phosphine oxides (50) and with one P—C bond to phosphonus acid derivatives (51). Chlorophosphines react rapidly with water, but aminophosphines, phosphinites and phosphonites often survive a short wash with aqueous NaHC03, an effective way to remove contaminating ammonium salts in the crude products. However, aminophosphines with small substituents, e.g. dimethylaminodimethylphosphine, aryl phosphinites and phosphonites and trimethylsilyl phosphinites and phosphonites are hydrolysed too quickly for such a treatment. The hydrolyses are catalysed by acids (the hydrolyses of phosphinites and phosphonites are also catalysed by OH ) and are much faster than hydrolyses of the corresponding phosphoryl compounds [up to a factor of 10 for acid-catalysed hydrolysis of (MeO)3P compared with (MeO)3P=0 ]. Dialkyl phosphonites are rapidly hydrolysed to the monoalkyl esters (51, X = OR) in weakly acidic water, whereas hydrolyses to phosphonous acids require reflux with strong acid or base, e.g. equation 131 Bis-(dialkylamino) phosphines may also be partially hydrolysed to phosphonous acid amides (51, X = NR2). Tervalent phosphorus acid derivatives with hydrogen sulphide give secondary phosphine sulphides or phosphonodithious acids, e.g. equation 156 . ... 

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). " ... 

Thus the enantioselective oxidation of P-racemic tertiary phosphines and aminophosphines was successfully attained by treatment with tetrahalomethanes and an alcohol. Oxidation of iV-phosphorylated amino acids by these reactants proceeded diastereoselectively with formation of aminophosphinates 131 in 80-85% yields and with 50-98% de. The compounds were purified by crystallization and obtained in optically pure form (>99% de) (Scheme 40) [33, 39]. 

Ring opening of 116 with t-BuLi and subsequent acidolysis with / -toluene-sulfonic acid (PTSA) afforded the secondary phosphine oxide 117 in 40% overall yield but with an interesting 85% ee. This reaction is noteworthy because the reader will probably remember that the acidolysis (either with Me0H/H2S04 or with dry HCl) of t-Bu substituted aminophosphine boranes does not occur (see Section 4.3.2). 

Entry 1 shows that low to moderate enantioselectivities can be obtained with simple monodentate phosphines whereas low enantioselectivities have been obtained with the P,N ligand of entry 2 or with the pincer ligand of entry 3. Much better results have been obtained with p-aminophosphines and their oxides (entries 4-6). Interestingly, it has been found that phosphine oxides provide better activities and similar enantioselectivities than trivalent phos-... 

Palacios et al. described the stereoselective synthesis of fluoroalkyl-substituted aziridine-phosphine oxides by the diastereoselective addition of Grignard reagents to functionalized ketoxime-phosphine oxides. Aziridines were used as intermediates for the regioselective S5mthesis of fluorine containing P-aminophosphine oxides. Products of the latter type could also be obtained by reduction of the ketoxime-phosphine oxides with sodium borohydride (Scheme 39). ... 

The asymmetric addition of secondary phosphine oxides to imines for the synthesis of enantioenriched a-aminophosphine oxides has been reported (Scheme 4.42) [93]. 

Scheme 52). Cherkasov et ah also studied the bis(Kabachnik-Fields) reaction and recent results of the Kabachnik-Fields reaction including the preparation of a-aminophosphine oxides have been reviewed. p-Aminophosphine oxides were obtained by the addition of primary and secondary amines to diphenyl(vinyl)phosphine oxide in water as the reaction medium (Scheme 53). ... 

An interesting synthetic approach to thietanes is the selective desulfurization of cyclic disulfides.The treatment of dithiolanes with a diethyl-aminophosphine results in a ring contraction to thietanes, (Eq. 19). This has been demonstrated with a-lipoic acid, a coenzyme with a dithiolane structure involved in the biological oxidation of pyruvic acid. The reaction is proposed to be initiated by the electrophilic attack of the phosphorus on the ring sulfur atom, resulting in the formation of an acyclic internal phosphonium salt, which by subsequent elimination of a phosphine sulfide, closes to the four-membered ring. °... 

In what is effectively a desulfurization reaction, 1,2-dithiolane 1,1-dioxide reacts exothermically with aminophosphines such as tris(diethylamino)phosphine in benzene solution to give 1,2-oxathiolane 1-oxide in excellent yield (71JOC322). The reaction, which requires a slight excess of the aminophosphine, is shown in Scheme 41. 

Studies of Equilibria, Reactions, and Solvent Effects.—Lanthanide shift reagents have been found to be effective for phosphines and phosphoryl compounds, but not for thiophosphoryl compounds. - In a comparison of various shift reagents, europium nitrate hexadeuterium oxide (26) was found to give large shifts of 8 for phosphates and phosphonates. A contact contribution to the Sp shifts was established. When there are two possible sites for co-ordination, as in the aminophosphine (27), steric effects play an important role. Co-ordination occurs at nitrogen in (27 R = H) but at phosphorus in (27 R = Me). The n.m.r. parameters... 

Aminophosphines. The synthesis and use of aminophosphines as ligands have been reviewed. Raeemie ehlorophosphines of the type R R PCl have been shown to react stereoselectively with chiral amines (1-phenylethylamine or aminoacid esters) in the presence of triethylamine to give the diastereomerically enriched aminophosphines (137), which were isolated as diastereomerically pure crystalhne borane complexes. This approach has also been used in the synthesis of chiral t-butylphenylphosphine oxide, via the acid hydrolysis of an intermediate chiral aminophosphine. Among other new mon-oaminophosphines prepared by treatment of primary or secondary amines with ehlorophosphines in the presence of a base are the adenine derivatives (138), the phosphinoalkylaminophosphines (139), " the aminophosphine-phosphine... 

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