Dialkyl phosphites, rearrangement

An unusual approach toward the preparation of a-bisphospho-nates began by treatment of an oxime with a phosphorus nucleophile (trialkyl or dialkyl phosphite) and phosphorus oxychloride (as promoter).354 The oxime undergoes a Beckman rearrangement the phosphorus nucleophile attacks the intermediate cation leading to an imine, which is then further attacked by the phosphorus nucleophile to give the a-bisphosphonate (Equation 3.21). 

Dialkyl phosphite addition to quinone monoimine species, followed by elimination and rearrangement (Figure 6.7).23... 

A photochemical Arbuzov rearrangement occurs on UV radiation of benzyl dialkyl phosphites, e.g. (162). The reaction has been shown to be largely intramolecular with migrating carbon, and also retention at phosphorus. 

The use of NiCl2 catalysts in the rearrangement of allylic phosphites (and related compounds) to allylic phosphonic (or phosphinic) acids has already been reported (Organophosphorus Chemistry, 1988, 1, 144), and the same authors have now described the use of Ni(cyclooctadiene) catalysts in the presence of bistrimethylsilylacetamide in the reactions between allylic esters,or carbonates, and dialkyl phosphites, monoalkyl alkylphosphonates,or monoalkyl... 

Rare examples of normal Michaelis-Becker reactions which involve co-chloroalkanal diethyl acetals are to be found, and although the formation of dialkyl acylphosphonates from sodium dialkyl phosphites and, for example, benzoyl chloride, is to be observed at -85 °C, the system is further complicated, even at -10 °C, by further addition steps followed by rearrangements which would seem to render the process of little value for the synthesis of oxoalkyl phosphonic esters On the other hand, in a more detailed and systematic study of reactions between sodium dialkyl phosphites, (RO)2PONa(R = Et or Bu), and the ketones R CO(CH2) Cl, Sturtz and others have observed the formation of epoxides when n = 1 and (1-hydroxy alk-2-enyl)phosphonic diesters when n = 2(R = Me or Pr ), according to the displacement in 532, and of derivatives of tetrahydrofuran or tetrahy-dropyran, according to 533 n = 3 or 4) when R = Et, the formation of the cyclic ethers was accompanied by low yields of the expected (oxoalkyl)phosphonic diester, but otherwise the latter were isolated as a single product only for R = Me, n = 5, and R = Et or Pr when n = 2. 

When the preparation of alkali metal enolates derived from alkanoylphosphonates was attempted by treatment with strong anhydrous bases such as lithium diisopropylamide or sodium hydride, the formation of phosphate phosphonate-type products was observed. This was interpreted in terms of fragmentation of the enolate formed in the first step to ketene and dialkyl phosphite anion (equation 75), and addition of the latter to the carbonyl group of an unreacted acylphosphonate molecules to form a bisphosphonate. Such molecules are known to rearrange to phosphate phosphonates ... 

The tetracoordinated lanthanide amides have been reported as catalysts for the phospho-aldol-Brook rearrangement reaction of dialkyl phosphites and isatins. ... 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Two reports are available on the rearrangement of mixed vinyl phosphite esters to produce phosphonate diesters in moderate yield.94 95 In both instances, the vinyl phosphite esters were prepared by reaction of the dialkyl phosphorous chloride with highly enolized carbonyl compounds. The mixed ester products undergo thermal rearrangement to the phosphonate diesters (Figure 6.25). 

Keywords alkyl chloride, trialkyl phosphite, alumina, microwave irradiation, Arbuzov rearrangement, dialkyl alkylphosphonate... 

Examples of the reaction of tervalent phosphorus with isocyanates and their analogues include the addition of phosphites to carbonyl isothio- and isoseleno-cyanates to give the phosphonates (32) and the reaction of dialkyl phosphoramidites with trichloroacetyl isocyanate to give the rearranged product (33). Predictably, the betaine (34) is obtained from the reaction of TDAP with fluorosulphonyl isocyanate more surprising is the relative stability of (34) to hydrolysis. ... 

Two variants of this rearrangement have been reported. One uses triethyl phosphite instead of diethyl chlorophosphite. Thus, in the presence of a catalytic amount of para-toluenesulfonic acid, triethyl phosphite reacts with propargyl alcohol in DMF at room temperature to give a mixture of diethyl allenylphosphonate (51%) and diethyl 1-propynylphosphonate (14%). The second variant is based on the conversion of dialkyl allenylphosphonates (R , R H, R = H, Scheme 1.19) into dialkyl 1-alkynylphosphonates by a photochemically allowed [l,3s]-sigmatropic shift in ( ,11, with 46-50% yields. ... 

Alkylation of dialkyl cyanomethylphosphonates gives somewhat higher yields of oc-substituted cyanomethylphosphonates than those obtained by Michaelis-Arbuzov rearrangement from trialkyl phosphites and substituted haloacetonitriles. 

The formation of the dialkyl (2-oxoalkyl)phosphonates (539) illustrates the regioselec-tive nucleophilic attack by phosphite anion, with rearrangement and displacement of sulphinate anion, applicable when R = C1-C5 alkyl and R = H, Me or Ph in the single case when Ar = Ph, R = H and R = Ph, the product was diethyl (2-phenylethenyl)phospho-... 

It has also been shown that dialkyl phosphonites give similar phosphoranes with dimethyl acetylene dicarboxylate <87PS(29)123>. These products are less stable than those from phosphites, and undergo the [1,5] rearrangement at -50°C. 

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