Hypophosphite esters

Maier, L., The addition of hypophosphite esters to activated olefins, a new method for preparing substituted ethyl phosphinates, Helv. Chim. Acta, 56, 489, 1973. 

Reduction of nitroalkenes. Vinyl nitro compounds are reduced to saturated ketones or aldehydes by Raney nickel and an aqueous solution of sodium hypophosphite. Ester groups, C=C bonds, and aryl NO, and halo groups are not reduced. Under these conditions nitroalkanes arc reduced to amines, and oximes are converted into carbonyl compounds in high yield. 

In the simplest form of the Abramov reaction, the phosphorus-containing reactant is hypophosphorous acid (phosphinic acid) or an ester thereof, and in the reactions between the acid and formaldehyde or benzaldehyde the initial product is the phosphinic acid 144 (R = H or Ph.). However, the reaction can proceed further to give the bis(l-hydroxyalkyl)phosphinic acid (145 R = H or Ph) the latter (R = Ph) reacts readily with yet more benzaldehyde to give its benzylidene derivative, 5-hydroxy-2,4,6-triphenyl-1,3,5-dioxaphosphorinane 5-oxide (146 R = Ph). When acted on by a second mole of cyclohexanone in the presence of acetyl chloride, (l-hydroxycyclohexyl)phosphinic acid (147) gives the novel phosphinic chloride 148, characterized as the free acid 149 following ready hydrolysis A reaction between a phosphinic acid (150) and a second (non-identical) carbonyl compound leads to an unsymmetrical phosphinic acid (151). Esters of symmetrical 1, r-dihydroxy-substituted phosphinic acids are preparable from hypophosphite esters, H2P(0)0R ". ... 

The combination of 1 mol of bis(trimethylsilyl) hypophosphite, 2 mol of an aldehyde or ketone and 1 mol each of chlorotrimethylsilane and triethylamine, affords bis[l-(trimethylsilyloxy)]phosphinic acids (218) according to Scheme 18, and subsequent ethanolysis then liberates the free hydroxyalkyl acids The same hypophosphite ester is reactive towards halogenoacetones, RCOCX X X (Scheme 19) the initial stage is a Perkow type of process yielding a trimethylsilyl alkenyl phosphinate ester, 219. This latter ester is reactive to chlorotrimethylsilane-Et3N to yield the bis(trimethylsilyl) alkenyl... 

Hypophosphite esters add to olefins, aldehydes and ketones (6.215) in the same way as hypo-phosphorous acid (6.209-6.211). 

Hypophosphite Esters. Methyl hypophosphite has been prepared by the reaction between Hypophosphorous Acid and 2,2-dimethoxypropane (eq 11)." However, the product reacts further with the acetone formed to give 1-hydroxy-1,1-dimethylmethylphosphinate (eq 12). 

Two preparations of diesters of phosphonous acid have been reported, - One of these, which claims to be the first preparation of these derivatives, involves the reaction of ammonium hypophosphite with triaikylsilylamines to give bis(trialkylsilyl) esters (127) in excellent yield. These compounds are extremely reactive, e.g. they are spontaneously inflammable in air. Dialkyl phosphonites (128) have also been prepared by the reduction of... 

The phosphites, and possibly the hypophosphites, are also capable of existing as tervalent forms which can be fixed as the esters, such as P(OEt)3, and according to the evidence of X-rays these forms predominate in the solid or liquid compounds, whereas in solution they change into the unsymmetrical tautomeric forms. The evidence is discussed under that section which is devoted to the acids in question. 

Violent reacdon with Al, BP, cyanide, esters, PN2H, P, NaCN, SnCb, sodium hypophosphite, thiocyanates. Dangerous disaster hazard due to fire and explosion hazard. When heated to decomposidon it emits toxic fumes of NOx. They are powerful oxidizing agents that may cause violent reacdon with reducing materials. Nitrates should be protected carefully in storage. 

The cellulose esters obtained are only slightly stable to the action of hydrolyzing agents. For example, boiling for 30 min in distilled water causes the phosphorus content of a cellulose hypophosphite to fall from 46-1.2% on boiling for one hour, it drops to 0.51 %. 

More recently, the related indium-mediated radical reactions have been widely studied (Scheme 7.13).19 Indium iodide-mediated radical cyclisation was first reported by Cook et al.20 The indium-mediated 1,4-addition of alkyl radicals to (F)-but-2-enenitrile was investigated by using 1-ethylpiperidinum hypophosphite (EPHP) as a hydrogen donor in aqueous media (Scheme 7.13).21 Atom transfer radical cyclisation and reductive radical cyclisation were studied using indium and iodine.22 Indium mediated alkyl radical addition to dehydroamino acid derivatives was also reported.23 The indium-mediated radical ring expansion of a-halomethyl cyclic (3-keto esters, shown in Scheme 7.13, was achieved in aqueous alcohols.24... 

COBALT BIS(NITRATE) (10141-05-6 10026-22-9, hexahydrate) A strong oxidizer. Violent reaction with reducing agents, powdered aluminum, ammonium hexa-cyanoferrate(ll), boron phosphide, carbon, combustible materials, cyanide, esters, fuels, organic materials, sodium hypophosphite, phosphorus, sodium cyanide, stannous chloride, thiocyanates. Incompatible with acetylene. 

P-Ketoesters. /3,y-Unsaturated )3-nitro esters undergo reductive Nef reaction in the presence of Raney nickel and sodium hypophosphite in a buffered medium. 

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