Hydrogen phosphinates

Examples SCN (thiocyanate), HSCN (hydrogen thiocyanate or thiocyanic acid), HNCO (hydrogen isocyanate), HONC (hydrogen fulminate), and HPH202 (hydrogen phosphinate). 

Addition of Hydrogen Phosphinates and Extension to Synthesis of P-Chiral Phosphinates. 50... 

As expected, hydrogen phosphinate, which is a hybrid structure of hydrogen phosphonate and secondary phosphine oxide, adds to alkynes in the presence of the Pd-diphenylphosphinic acid catalyst system (Scheme 44) [36]. Normally, branched isomers are the major products, while trimethylsily-lacetylene exceptionally affords the corresponding terminally phosphinylat-ed product. Diphenylacetylene also reacts to afford the corresponding adduct in 99% yield. 

Synthesis of Hydrogen Phosphinate Amino Acid Analogues... 

An aldehyde (1 mmol), dissolved in an equal volume of dry dioxane, was added under N2 to a suspension of an equimolar amount of the phosphinic acid salt of DpmNH2 in dry dioxane (10-20mLg ) at 100°C under N2, at such a rate that the temperature at reflux remained at ca. 100 °C. H20 was removed azeotropically with dioxane. When two thirds of the dioxane had been removed by distillation, the mixture was cooled to rt and diluted with an equal volume of abs EtOH. The hydrogen phosphinic acid 32 crystallized slowly and was collected by filtration, washed successively with EtOH and Et20, and dried. 

In addition to the conversion into phosphonochloridates as described in Section 10.10.2.1.2, phosphonate monoacids can also be activated for coupling via some of the popular reagents from standard peptide chemistry, such as BroP, 77 BOP/ and PyBOP. 79 One-pot activation and coupling of hydrogen phosphinates with a-hydroxy acids is also possible via the method outlined in Section 10.10.2.1.3. 76 The procedure outlined in Scheme 19 illustrates an optimized procedure for coupling a hindered phosphonate 57 and an a-hydroxy acid derivative via the phosphonochloridate 72 ... 

New y-ethoxycarbonyl- and ot-amino-alkyl-hydroxyphosphinic acid derivatives (366) and (367) were conveniently prepared by Michael addition or Kabachnik-Fields reaction of a new precursor, benzyloxymethyl hydrogen-phosphinate (368), with a,p-unsaturated esters or imines (Scheme 94). " Phosphinic acid inhibitors (369) of Cathepsin C were synthesized by addition of methyl acrylate to the appropriate a-amino phosphinic acid and by... 

Bochwic, B., and Michalski, J., Eormation of C-P bonds by addition of di-alkyl hydrogen phosphonates and alkyl hydrogen phosphinates to activated ethylenic derivatives. Nature, 167, 1035, 1951. 

ZnO hydrogen, phosphine thick film, thin film [26]... 

Reaction of white phosphorus with sodium hydroxide or sodium eth-oxide in ethanol generates a dark red solution of an uncharacterized metastable phosphorus compound (9) which possesses nucleophilic properties (10). The red product decomposes slowly even at 0 to hydrogen, phosphine, and sodium hypophosphite (9). But addition of methyl iodide to the freshly prepared solution is reported to give methylphos-phine, methylphosphonic acid, dimethylphosphinic acid, and trimethyl-phosphine oxide (10). Analogous products were reported from reaction with isoamyl iodide, where isoamylphosphonic acid was obtained in 59% yield based on the iodide. 

Carbon-phosphorus bonds can be formed by the addition of dialkyl hydrogen phosphites or alkyl hydrogen phosphinates to activated ethylenic compounds. ... 

Silicomanganese is an alloy based on manganese, silicon, and carbon along with some impurities. On contact with moisture it can generate hydrogen, phosphine, and arsine gases. 

The cyclic hydrogen phosphinate can also be added to benzoquinone to make a substituted hydroquinone and a diglycidyl ether therefrom, discussed below in connection with epoxy resins. 

This is an addition product of a hydrogen phosphinate with dimethyl ita-conate. A diol with the same ring system can also be used to make other phosphorus-containing thermoplastic polyesters (167). 

The hydrogen phosphinate itself can be reacted directly into epoxy resins to produce presumably a j8-hydroxyphosphinate structure (188) however, this consumes epoxy fimctionality and creates chain ends which tend to reduce the Tg. 

A more selective means for incorporation of this ring system is to react the hydrogen phosphinate with benzoquinone by reductive addition to produce the phosphinyl-substituted hydroquinone (189,190). This can be used as a chain... 

The last of this series of experiments was a study of the phosphorisation of steels. Phosphorisation occurred on heating the steel sample in a hydrogen-phosphine mixture, and concentration gradients of phosphorus into the metal were established. It was found on analysing the cpncentration-distance curves that carbon retarded the diffusion of phosphorus very strongly, and that phosphorus entering the metal swept the carbon in front of it. 

The addition of resolved P-chiral hydrogen phosphinates to alkenes has been accomplished without significant loss of the stereochemistry at phosphorus (Scheme 4.84) [124]. This reaction was achieved with the use of a radical initiator. One of the attractive aspects of this chemistry was that it proceeded under solvent-free conditions. The reaction was regioselective for the anti-Markovnikov product, and fair to moderate yields of the alkyl-phosphinate were obtained. Generally, high yields of the alkylphosphinate were obtained for a host of terminal alkenes as well as strained internal alkenes such as norbomene. Internal alkenes were significantly less reactive and satisfactory conversions were only... 

Montchamp followed up this work with the development of a catalyst system for the cross-coupling of hydrogen phosphinate esters with arylhalides (Scheme 4.224) [380]. While several aryl halides were screened in this chemistry, aryl chlorides were the focus of the investigation as they are typically sluggish in Hirao-type cross-coupling reactions. 

SCHEME 4.224 Palladium-catalyzed cross-coupling of aryl chlorides with hydrogen phosphinate esters [380]. 

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