Hypophosphite, addition

The remaining 15% of the elemental P is used in P -dependent apphcations which require the element as a direct reactant. The principal products include P2S5, PCl and POCl, 2 5 hypophosphite, with much smaller amounts leading to PH, red P, phosphonates, and various other phosphoms derivatives. Pinal apphcations include flame retardants (qv), lubricant additives, insecticides, herbicides, water treatment, cleaning compounds, plastici2ers, and semiconductors (14). 

In addition, a small amount of decomposition of hypophosphite by alkaU occurs. 

Sodium borohydride or dimethylarnine borane have found limited use as reduciag agents because of expense. In addition, bath stabiHty, plating rate, and deposit properties are inferior to those of formaldehyde-reduced baths. The deposit is a copper—boron alloy. Copper—hypophosphite baths have been iavestigated, but these are poorly autocatalytic, and deposit only very thin coatings. 

Dibasic forms of phosphorus (III) species also have been reported to undergo Michael-type additions to unsaturated substrates. Hypo-phosphorous acid adds to acrylamides to generate free phosphonous acids in good yield,430 as well as to vinyl acetate.431 Further, methyl hypophosphite adds to a variety of unsaturated substrates,432 as does the ammonium salt of mono(2-ethylhexyl) phosphite (Equation 3.27).433... 

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

The addition of hypophosphites to alkenes under Et3B initiation is also reported [27]. Piettre described recently the addition of diethylthiophosphite to alkenes leading to the formation of thiophosphonates (Scheme 9, Eq. 9a) [28]. Interestingly, this reaction can be used for cyclization of dienes and ring opening of strained alkenes such as a-pinene (Eq. 9b). Parson prepared an... 

The usual flood of reports concerning the addition of phosphites to imines has appeared. These include the reaction of hypophosphites to give a-aminoalkyl-phosphinic acid salts possessing antibacterial activity22 and the synthesis of AM, 4,2-A5-oxazaphospholines (30) from phosphites and carboxamides.23 The addition of... 

Gallagher has reported a convenient synthesis of functionalized phosphorinans (102) by Michael addition of methyl hypophosphite to methyl acrylate, followed by base-induced cyclization.78... 

Pure arsenic has been prepared by reducing carefully purified ammonium dihydrogen arsenate at 1000° C. in a current of ammonia, the arsenic being finally resublimed in a vacuum.7 The element may also be obtained as an amorphous precipitate by reduction of aqueous arsenious acid, for example, by means of sodium hypophosphite,8 or by the addition of a few drops of phosphorus trichloride.9 The reaction in the latter case probably takes the following course ... 

Addition across the P—P and P—C bonds. Tetraethyl hypophosphite was successfuly added to la. Upon subsequent air oxidation the diphosphonate 35, and a significant amount of the more complex structure 36 were isolated48,104 (equation 18). 

Rapid reduction of aromatic nitro compounds into amines has been described using sodium hypophosphite and FeSC>4-7H20. The reactions showed best results in terms of yields and purity, when the substrates were pre-absorbed on alumina and irradiated by microwaves under solvent-free conditions. The reaction is chemoselective and does not affect functional groups such as CN, OH, COOH, CONH2 or halogens. In addition, oximes were not reduced under the given reaction conditions, but were dehydrated to the corresponding nitriles instead (Scheme 4.32)57. 

White phosphorus also may be hydrolyzed in an alkaline aqueous environment with the addition of heat (see Figure 2-3) to give a mixture of hypophosphite and phosphite, with hydrogen and phosphine, respectively, as co-products (Cotton and Wilkinson 1966). Hudson... 

Hydroxycodeinone (4.98 g) and acetic acid (137 g) were added to a reaction flask (3-neck, 250 ml) equipped with mechanical stirrer, addition funnel, thermocouple and nitrogen-inlet adapter. The system was evacuated and the flask filled with nitrogen. Subsequently, 5% Pd/C (50% water wet, 3.0 g) in one portion was added under the nitrogen atmosphere. While the mixture was stirred for about 5 min at ambient temperature, a solution of sodium hypophosphite (6.0 g) in deionized water (25 g) was prepared. The aqueous sodium hypophosphite solution was transferred into the addition funnel, and added to the reaction mixture over a period of about 30 min at about 22°C. The mixture was then warmed to about 45°C and stirred for about 1 hour. 

Additional preparations of hypophosphite analogs are indicated in the reactions which are given below. 

The amount of hypophosphite oxidised per unit time is proportional to the weight of catalyst present. Sodium hydroxide, hydrochloric and sulphuric acids, each retard the reaction, whilst the addition of sodium hydrogen carbonate either is without action or slightly enhances the velocity of reaction.2... 

A hypophosphite solution is acidified with dilute sulphuric acid, treated with a known amount, in excess, of decinormal iodine solution and allowed to stand for 10 hours at ordinary temperatures. A cream of NaHCOg is then added until C02 evolution ceases, then fifth-normal NaHC03 solution, saturated with C02, whereby oxidation goes through the next stage, to phosphate. After addition of acetic acid the excess of iodine is titrated with standard arsenite as before. 

Where colour reactions are to be observed, it is recommended that the hydriodic acid be decolourized by the addition of 1-2 per cent by volume of SO per cent hypophosphorous acid or by warming with a little potassium hypophosphite. 

Cupric hypophosphite, Ch HgPOg) —The solution obtained by addition of slightly less than the equivalent proportion of barium hypo-phosphite to a solution of cupric sulphate yields, after removal of the barium sulphate and addition of alcohol, the hypophosphite in the form of white crystals.4 At ordinary temperatures the dry salt does not decompose for several days, but at 90° C. it explodes with evolution of phosphine. On warming in aqueous solution, it decomposes with formation of phosphorous acid, copper, and hydrogen. Its aqueous solution is also decomposed catalytically by palladium ... 

Sitrile — aldehyde (1, 725-726 2,293). The nitriles 1 and 2 are reduced with W2 Raney nickel in a slightly acidic buffer system to give the corresponding aldehydes in 72-74% yield. Additional reducing agents (sodium hypophosphite, formic acid, or H2), which are commonly needed in similar reactions, are not required. 

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