Phosphinic esters

Neutral Extractants. Many neutral organophosphoms extractants are available phosphate esters, phosphonate esters, phosphinate esters, and phosphine oxides. The most popular neutral extractant is tributylphosphate (TBP), which reacts with RE elements according to a solvation mechanism ... 

The l l-adducts obtained from the ethylene phosphonothioites (38 R = Ph or Bu ) with diacetyl, benzylideneacetylacetone, and phen-anthraquinone readily eliminate ethylene sulphide to give the corresponding phosphonate or phosphinate esters. The benzylideneacetylacetone adduct of (38 R = Bu ) contained the two diastereoisomers (39) and (40) which, on elimination of ethylene sulphide at 100 °C, gave isomeric phosphinates. 

C. Reactions of Phosphoric and Phosphinic Acid Derivatives.—The optically active phosphinate ester (90) has been shown to react with benzyl Grignard reagents or lithium anilide with inversion of configuration. Oxidation of... 

The non-equivalence of the ester protons in the monomethyl- and monophenyl-phosphinic ester function, as in (44, Ch = chalkogen), has been studied. Compounds of type (45) have some interesting stereochemistry. They are prepared from racemic secondary butyl alcohol, and the presence of three signals in the P n.m.r. spectrum confirms that the phosphorus atom is the centre of pseudo-asymmetry. A 1 2 1 triplet is observed which is attributed to the presence of equal amounts of two mesa forms, (45) and (46), which have different values of Sp (outer peaks), and two racemic forms, (47) and (48), which have identical values of 8p (central peak). 

Anthryl, 1-naphthyl, mesityl, and 4-quinolyl groups in 37h-k promote C/C aryl shift (see Table 2) their proclivity to migrate is far greater than expected from the electronic influence of the x-systems. This is presumably due to the intermediacy of spiro-linked benzenium betaines 30 31 , occurring in place of the carbenes otherwise encountered. The formation of phosphinic esters 42h-k is partly or completely suppressed 30). 

The same reaction sequence performed in methanol affords a mixture of diastereo-mers of the phosphorylated phosphinic ester 48b, of which one pure isomer can be isolated32 . In the presence of piperidine, reductive elimination of nitrogen 28,29) from 45 to give bis(diphenylphosphoryI)methane competes with the prevailing formation of the phosphinic piperidide 48c32). Expected trapping of 47 by [2 + 2]-cycloaddition with benzaldehyde fails to occur in place of 1,2k5-oxaphosphetanes, products are obtained which arise mainly by way of the benzoyl radical32,33). 

Photolysis of the first known cyclic a-diazo-p-oxophosphine oxide 49 is unsuccessful with regard to phosphene formation. There is no evidence for a P/C-phenyl shift, which should lead to 51, nor for a P/C-alkyl shift, which would afford 52 via ring contraction, since none of the expected phosphinic esters could be isolated in methanolM). 

Aryldioxophosphoranes such as aryl- and alkyl-iminooxophosphoranes number among the short-lived metaphosphonates. The former are best obtained by fragmentation of cyclic phosphinic esters, and the latter by rearrangement of aryl- and alkyl-substituted phosphoryl azides and nitrenes, respectively. This reaction is reminiscent of the phosphorylcarbene/methyleneoxophosphorane rearrangement discussed in Section 2. 

The hydrohalogenation of phenyl(3-methyl-l,2-butadienyl) phosphinic esters involved protophilic attack of the reagent, followed by heterocyclization of the allenephosphonate system (Scheme 40) [103, 104],... 

Figure 17.24 The traceless Staudinger reaction can be used to form larger peptides from smaller peptides, if one contains an azido group at the N-terminal and the other one contains a phosphine ester at its C-terminal. The reaction gives a native peptide (amide) bond with loss of the phosphine group.

The FCLD has been particularly useful as a highly sensitive means of measuring volatile sulfur, selenium, and tellurium compounds in studies of bacterial methylation [67, 111-114], Because of its high sensitivity to phosphinate esters [68], the FCLD could potentially serve as a monitor for nerve gases. 

Preparation of ethyl methyl(2-carbomethoxy-3-phenylpropyl)phosphinate — Addition of a monobasic phosphinous ester to an unsaturated ester in the presence of a silylating agent... 

The acid-catalysed hydrolysis of phosphinic esters (158) is relatively insensitive to the substituent (R = Me, Et, Pr1, or Bu1) attached to phosphorus this contrasts with the base-catalysed process.126 The acid hydrolysis of the phosphinic esters (159) (see Organophosphorus Chemistry , Vol. 7, p. 129 for the base hydrolysis) takes place with alkyl-oxygen fission in an SnI process.127... 

The ax-membered spiro compound 210 reacts with H202/LiBr/HAc to form besides some byproducts the stereoisomeric 4-hydroxy-3 -bromopropyl-phosphinic esters 211 Z and E. This experiment of Stade strengthens the proposed mechanism for oxidative dealkylation formulated above. 

When l,l-dimethoxy-4-propyl-2,6-diphenyl-A5-phosphorin (53) is transformed into its 4-carbenium tetrafluoroborate (54) and treated with a base the 4-(l-propenyl) derivative (55) is formed. This, by a two phase oxidation with KMn04, gives the aldehyde (56) which can be further transformed, e.g. into the nitrile (57 equation 34) (75AG(E)lll). An Arbusov type dealkylation of the cation salts (49) (or 54) with LiBr gives the phosphinic ester (58 equation (35)). 

All of the bisphosphines in Table I were prepared by the reaction of the appropriate Grignard reagent on a resolved menthyl phosphinate ester as described in our previous work (3). R was either phenyl (II) or o-anisyl (3). Rx corresponds to Ri group in Table I. 

Mol. wt. 340.27, m.p. 125-127°. The phosphinic ester is prepared by reaction of diphenylphosphinyl chloride and 2-hydroxy-5-nitropyridine in the presence of triethylamine. 

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