Phosphane/phosphine reactions

In a similar way to the aminolysis of the P-N bond mentioned above (Scheme 9), alcoholysis of phosphinous amides leads to the alkyl esters of the respective phosphinous acids [30, 121]. This reaction occurs with inversion of the absolute configuration of the phosphorus atom, and has been used in a synthetic sequence leading to optically active tertiary phosphanes 22 [122] (Scheme 23). 

Sugar derivatives of phosphanes can be made by reaction of ethylene glycol derivatives with sugar diacetonides to form monoallyl ethers, which can be brominated at the double bond. These compounds react with phenyl-and diphenylphosphanes to yield ligands with a sugar function in the side chain (57). Phosphinated glucopyranosides were prepared by Oehme and... 

In recent years the synthesis of chiral and achiral tripodal phosphines and their application in homogeneous catalysis has been studied in more detail [2]. Enantiomerically pure tripodal ligands were synthesized from the corresponding trichloro compounds and chiral, cyclic lithio-phosphanes, e.g. 17, (Scheme 6) [21,22], Using a rhodium(I) complex of ligand 18, an enantiomeric excess of 89 % was obtained in the asymmetric hydrogenation reaction of methyl acetami-docinnamate (19). 

The use of Cp rings with pendant phosphines in CpCoL2 complexes has also been reviewed. Carbonyl complexes of this type (Cp Co(CO)2) lose CO at room temperature to afford pendant phosphane adducts (equation 46). The chelated phosphane can then be uncoordinated with ligands such as cod substitution of cod (Section 5.1.4) with alkynes allows the cobalt complex to participate in cychzation reactions (Scheme 26). 

One example is known in which the elements of a phosphinic acid are eliminated in the same reaction step. In the synthesis of (-f)-( / ,2/ )-[( )-hex-l-enyl]-2-vinylcyclopropane [(-E)-dic-tyopterene, 4] and its (—)-enantiomer, the ji-oxo phosphane oxide 2 obtained by condensation of pentyidiphenylphosphane oxide with methyl 2-vinylcyclopropanecarboxylate (1) was first reduced to the corresponding /(-hydroxy phosphane oxide 3 and then treated with sodium hydride in dimethylformamide. This procedure gave the desired diene 4 and its enantiomer in 19 to 23% yield from the P-oxo phosphane oxide. The stereoselectivity was fairly good, giving 85% of the 5-isomer, which could be separated on silver-impregnated silica gel. ... 

Reaction of tris(2-pyridyl)phosphane (8) with chlorine in methylene dichloride or acetonitrile gave chlorotris(2-pyridyl)phosphonium chloride or its covalent isomer tris(2-pyridyl)phosphonium dichloride (20). Treatment of the dichloride derivative with dilute HCl afforded the coupling product, 2,2 -bipyridine (16), whereas tris(2-pyridyl)phosphine oxide (9) was isolated from the reaction with sodium hydroxide. 

Good yields of ligand coupling products were also obtained in the reaction of tris(2-pyridyl) phosphane or phosphine oxide with chlorine in methanol. 

Sterically more demanding phosphanes such as tris(< -toluene)phosphine introduce steric congestion to the transition state of the alkylation which resembles the initial product of this reaction, the complex of palladium(O) with the product alkene. Since the less sterically encumbered exocyclic complex A is energetically favored over the endocyclic complex B, a preferential attack of the nucleophile at the higher substituted endocyclic site results27,34. 

The co-production of isobutyraldehyde has always proved embarrassing, but the introduction of rhodium liganded with a phosphine (Union Carbide) or phosphane (Ruhrchemie/Rhone-Poulenc) as catalyst permits milder reaction conditions and gives -/iso-ratios of 8 1 or more (see section 11.7.8.2). 

Few silaphosphenes (phosphasilenes, silylene phosphines, silylidene phosphanes) have as yet been isolated. They are formed as intermediate species in reactions of type (9.251). First evidence was obtained in 1979 with the reaction (9.252) [49]. A stable compound is formed in Equation 9.251 when large protecting groups are present. 

Alkylation at Phosphorus. Phosphines and phosphites undergo easy quaternization. Thus methylation of tris(2,6-dimethyl-phenoxy)phosphine with MeOTf, followed by treatment of the product with sodium 2,6-dimethylphenoxide, gave methyltetrakis (2,6-dimethylphenoxy)phosphane. Methoxyphosphonium tri-flates are relatively stable intermediates in Arbuzov reactions Phosphine oxides and sulfides are alkylated. S-Methylation of chiral phosphine sulfides, followed by treatment with hexam-ethylphosphorous triamide, has been advocated as a general synthesis of optically active phosphines. ... 

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