Phosphites organic, from phosphorus

The P-H bond is also weak enough to serve in thione-based radical chemistry. The first success was achieved with dialkyl phosphites [40a]. However, hypophosphorous acid and its salts proved to be even better [40b]. In a final paper [40c], the various phosphorus-based reagents were compared. The crystalline salt N-ethylpiperidine hypophosphite was very convenient and has been commercialized 140c]. The use of hypophosphorous acid has the advantages of nontoxicity, cheapness, and ease of removal from the organic reduction products. It already has several industrial applications. 

Phosphites can be very easily prepared by the reaction of a phosphorus halide with alcohol and an organic base, typically triethylamine or pyridine.36 It is generally necessary to use low temperatures and to keep the reaction free from moisture and air. If diols are used, reaction conditions can be adjusted so that oxygen either... 

The particular syndrome of OPIDN is produced by certain organic compounds of pentacovalent phosphorus. The less common and relatively unstable organic compounds of trivalent phosphorus, such as triphenyl phosphite, can produce a different spatial-temporal pattern of neurodegeneration, which is distinct from OPIDN. 

We turn now to the comparison of phosphate esters with esters of other phosphorus oxyacids, namely phosphites, phosphonates and phos-phinates. Phosphites are distinguished from phosphates by a lower formal valence number (l.t. by a basically different bonding structure), whereas in phosphonates and phosphinates the phosphorus is formally pentavalent, as in phosphates. Phosphonates and phosphinates have direct carbon-phosphorus bonding, while the linkage of the organic groups in the phosphate esters is all of the carbon-oxygen-phosphorus type. 

Organic halides of other elements [tin (43-45), phosphorus (6,54), nitrogen (46,93,245,251), sulfur (232,233,252,256-259)1 also participateV in Michaelis-Arbuzov type reactions. Heating the organic lead compound EtsPbBr with (EtO)3P at 100° gave only an unidentified white amorphous solid (45). Petrov and SokoPskii (250), who observed the formation of phosphate esters from the reactions of ethyl hypochlorite with various phosphite esters, proposed the existence of a pentacovalent intermediate which decomposed by loss of alkyl halide. 

Besides phosphines and phosphites preferentially used as ligands in hydro-formylation, phosphoramidites have also been proposed. Phosphoramidites (sometimes also called phosphoroamidites) are a class of organic phosphorus compounds derived from phosphites in which the P-OR groups have been replaced by P-NR2 groups (Figure 2.31). Three different P-substituents produce a chiral (stereogenic) phosphorus atom. Phosphoramidites play a crucial role in the synthesis of nucleic acids [1] and have also been frequently considered as mono- or bidentate ligands in transition-metal catalysis [2]. 

---