Metal phosphites reaction with alkyl halides

Phosphites. The deprotonation of (7,0-dialky 1 phosphites (25) with KH or NaH generates metal phosphites (26), which can be reacted with CS2 followed by the reaction with alkyl halides to afford (7, (3-dialkyl phosphonodithioformates (27) (eq 18). The deprotonation with JCH is carried out at 0 °C for 3 h, whereas the reaction withNaH is performedinTHFatrefluxforS min. As alkyl halides, methyl iodide, trityl, fluorenyl, and benzyl bromides are used, and the products (27) are obtained in 65-85% yields. 

Alternatively, acyliron complexes can be obtained in a two-step sequence either from dicarbonyl(cyclopentadienyl)ferrates or from dicarbonyl(cyclopentadienyl)iron halides via alkyl-Fp complexes. The first method makes use of the nucleophilicity of [CpFe(CO)2] anions. Their reaction with alkyl halides provides alkyl-Fp complexes that, upon treatment with phosphanes or phosphites, undergo a migratory insertion of a carbonyl ligand into the metal-alkyl bond leading to an acyliron complex (Scheme 4-38). " ... 

Apart from their behaviour as ligands in metal catalyst systems, studies of the reactivity of phosphites towards a wide variety of other substrates have attracted attention. New aspects and applications of the classical Michaelis-Arbuzov reaction and its variants continue to appear. Evidence of the thermal disproportionation of methyltriaryloxyphosphonium halides formed in the reactions of triarylphosphites with alkyl halides, together with the formation of P-O-P intermediates, has been reported. The Michaelis-Arbuzov reaction has been used in the synthesis of phosphonate-based styrene-divinylbenzene resins and polyphosphonated chelation therapy ligands.Treatment of electron-rich benzylic alcohols dissolved in triethylphosphite with one equivalent of iodine affords a low-temperature one-pot route to the related benzylic phosphonates, compounds which are otherwise difficult to prepare. Upper-rim chloromethylated thiacalix[4]arenes have also been shown to undergo phosphonation on treatment with a phosphite ester in chloroform at room temperature. The nickel(II)-catalysed reaction of aryl halides with phosphite esters in high boiling solvents, e.g., diphenyl ether, (the Tavs reaction), has also... 

Phosphonates can be prepared relatively easily via the Arbusov reaction, i.e. the alkylation of trialkyl phosphites with alkyl halides [58], or the Michaelis reaction, which is the reaction of alkali metal derivatives of dialkyl phosphites with alkyl halides [59,60]. 

Apart from their behaviour as ligands in metal catalyst systems, studies of the reactivity of phosphites towards a wide variety of other substrates have attracted attention. New aspects and applications of the classical Michaelis-Arbuzov reaction and its variants continue to appear. Evidence of the thermal disproportionation of methyltriaryloxyphosphonium halides formed in the reactions of triarylphosphites with alkyl halides, together with the formation of P-O-P intermediates, has been reported. The Michaelis-Arbuzov reaction has been used in the synthesis of phosphonate-based styrene-divinylbenzene... 

The classical procedure, and the one still extensively employed, consists in the alkylation of compounds containing the P(0)H moiety, as an appropriate metal salt, with an alkyl halide or similar type of compound such a procedure can sometimes be a successful alternative when the classical Michaelis-Arbuzov reaction fails, one such example being illustrated in equation 19. No reaction takes place between triethyl phosphite and 3-chloro-cyclopentadiene at below 120 °C, above which the main reaction is then dehydrochlorination the use of sodium dialkyl phosphites leads, however, to the desired dialkyl cyclopent-2-enylphosphonates. ... 

Although it might be expected that reactions which employed triarylmethyl halides would occur very readily, such reactions are rendered potentially more complex by the known nature of the halides and their propensity for involvement in free radical reactions. Whereas normal alkylation proceeds between sodium diethyl phosphite and diphenyl-methyl halides, success, or otherwise, in the use of the triphenylmethyl halides depends to some extent on the individual halide and on the metal in the phosphite salt. Thus, in an early study (in 1939), Arbuzov found that in reactions between silver dialkyl phosphites and triphenylmethyl bromide, dialkyl triphenylmethylphosphonates were indeed formed, but the use of the corresponding alkyl chloride provided the phosphite triester instead (metal dialkyl phosphites possess ambident anions ). A later study confirmed the behaviour of the silver salts towards the chloride, but also showed that, whereas dialkyl phophites with primary alkyl groups yielded phosphonic diesters (as had already been found), those with secondary alkyl groups afforded phosphite triesters moreover, the presence and nature of aromatic substituents were also able to control the course of the reaction. Reactions which involve triarylmethyl halides and sodium dialkyl phosphites may well be of a free radical nature since repeated studies have demonstrated the forma-... 

Phosphines may be obtained by reaction with Grignard reagents (6.45), phosphites from reactions with alcohols (6.296,6.310) and phosphonic and phosphinic halides from reactions with metal alkyls (6.142,6.153) or other organic compounds (6.145-6.148,6.151,6.153). 

In the Michaelis reaction (which usually gives lower yields than the corresponding Arbusov reaction), a metal dialkylphosphite (dialkylphosphonate - see below) is reacted with an alkyl halide to give a dialkyl ester of an alkyl phosphonate (6.272). Alkyl p-toluene sulphonates or dialkyl sulphates may be used in place of alkyl halides. Esters of unsaturated phosphonic acids, containing OH and CO groups can be obtained from an unsaturated aldehyde and a dialkyl phosphite (6.273). 

In the alkyl chain hydroxy groups or side chains may be present. The reaction is somewhat different when acyl halides are used. Hydroxymethanediphosphonic acid is prepared by reacting phosgene with an alkali metal, dialkyl phosphite. The reaction is rapid and exothermic. The temperature is controlled between 10 and 20°C. After hydrolysis with HC1, hydroxymethanediphosphonic acid is recovered [91,92]. 

---