Diethylphosphite

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Diethylphosphite
(EtO)2POH.png
Names
Preferred IUPAC name
Diethyl phosphonate
Other names
diethyl phosphonite; DEP; Phosphonic acid, diethyl ester
Identifiers
3D model (JSmol)
4-01-00-01329
ChemSpider
ECHA InfoCard 100.010.992 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C4H11O3P/c1-3-6-8(5)7-4-2/h5H,3-4H2,1-2H3
    Key: SULWMEGSVQCTSK-UHFFFAOYSA-N
  • CCOP(O)OCC
Properties
C4H11O3P
Molar mass 138.103 g·mol−1
Appearancecolorless liquid
Density 1.072 g/cm3
Boiling point 50-51 °C at 2 mm Hg
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Diethyl phosphite is the organophosphorus compound with the formula (C2H5O)2P(O)H. It is a popular reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. Diethyl phosphite is a colorless liquid. [1] The molecule is tetrahedral.

Contents

Synthesis and properties

The compound was probably prepared in the 1850s by combining phosphorus trichloride and ethanol, but intentional preparations came later. It arises as follows: [2]

PCl3 + 3 C2H5OH → (C2H5O)2P(O)H + 2 HCl + C2H5Cl

Under similar conditions but in the presence of base, triethyl phosphite results: [3]

PCl3 + 3 EtOH + 3 R3N → P(OEt)3 + 3 R3NH + 3 Cl−

Many analogues of diethyl phosphite can be prepared. [4] [5] Despite being named as a phosphite the compound exists overwhelmingly in its phosphonate form, (C2H5O)2P(O)H, a property it shares with its parent acid phosphorous acid. Nonetheless many of its reactions appear to proceed via the minor phosphorus(III) tautomer. [6]

(C2H5O)2PIII(OH) ⇌ (C2H5O)2PV(O)H, K = 15 x 106 (25°C, aqueous) [7]

Reactions

Hydrolysis and alcoholysis

Diethyl phosphite hydrolyzes to give phosphorous acid. Hydrogen chloride accelerates this conversion.: [2]

Diethyl phosphite undergoes transesterification upon treating with an alcohol. For alcohols of high boiling points, the conversion can be driven by removal of ethanol: [8]

(C2H5O)2P(O)H + 2 ROH → (RO)2P(O)H + 2 C2H5OH

Similarly amines can displace ethoxide: [9]

(C2H5O)2P(O)H + RNH2 → (C2H5O)(RN(H)P(O)H + C2H5OH

P-alkylation

Diethyl phosphite undergoes deprotonation with potassium tert-butoxide. This reactivity allows alkylation at phosphorus (Michaelis–Becker reaction): [10]

(C2H5O)2P(O)H + KOtBu → (C2H5O)2P(O)K + HOtBu
(C2H5O)2P(O)K + RBr → (C2H5O)2P(O)R + KBr

For converting aryl halides, palladium-catalysis can be employed. [1] The C-P coupling process is reminiscent of the Buchwald-Hartwig amination.

Reaction of diethyl phosphite with Grignard reagents results in initial deprotonation followed by displacement of the ethoxy groups. [11] [12] This reactivity provides a route to secondary phosphine oxides, such as dimethylphosphine oxide as shown in the following pair of idealized equations:

(C2H5O)2P(O)H + CH3MgBr → (C2H5O)2P(O)MgBr + CH4
(C2H5O)2P(O)MgBr + 2 CH3MgBr → (CH3)2P(O)MgBr + 2 MgBr(OC2H5)
(CH3)2P(O)MgBr + H2O → (CH3)2P(O)H + MgBr(OH)

Hydrophosphonylation

Diethyl phosphite can add across unsaturated groups via a hydrophosphonylation reaction. For example, it adds to aldehydes in a manner similar to the Abramov reaction:

(C2H5O)2P(O)H + RCHO → (C2H5O)2P(O)CH(OH)R

It can also add to imines in the Pudovik reaction and Kabachnik–Fields reaction, [13] in both cases forming aminophosphonates

See also

Related Research Articles

<span class="mw-page-title-main">Phosphite anion</span> Ion

A phosphite anion or phosphite in inorganic chemistry usually refers to [HPO3]2− but includes [H2PO3]− ([HPO2(OH)]−). These anions are the conjugate bases of phosphorous acid (H3PO3). The corresponding salts, e.g. sodium phosphite (Na2HPO3) are reducing in character.

<span class="mw-page-title-main">Phosphorus trichloride</span> Chemical compound

Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic and reacts readily with water to release hydrogen chloride.

<span class="mw-page-title-main">Phosphorus tribromide</span> Chemical compound

Phosphorus tribromide is a colourless liquid with the formula PBr3. The liquid fumes in moist air due to hydrolysis and has a penetrating odour. It is used in the laboratory for the conversion of alcohols to alkyl bromides.

<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

<span class="mw-page-title-main">Michaelis–Arbuzov reaction</span>

The Michaelis–Arbuzov reaction is the chemical reaction of a trivalent phosphorus ester with an alkyl halide to form a pentavalent phosphorus species and another alkyl halide. The picture below shows the most common types of substrates undergoing the Arbuzov reaction; phosphite esters (1) react to form phosphonates (2), phosphonites (3) react to form phosphinates (4) and phosphinites (5) react to form phosphine oxides (6).

<span class="mw-page-title-main">Phosphorous acid</span> Chemical compound (H3PO4)

Phosphorous acid is the compound described by the formula H3PO3. This acid is diprotic, not triprotic as might be suggested by this formula. Phosphorous acid is an intermediate in the preparation of other phosphorus compounds. Organic derivatives of phosphorous acid, compounds with the formula RPO3H2, are called phosphonic acids.

<span class="mw-page-title-main">Phosphonate</span> Organic compound containing C–PO(OR)2 groups

In organic chemistry, phosphonates or phosphonic acids are organophosphorus compounds containing C−PO(OR)2 groups. Phosphonic acids, typically handled as salts, are generally nonvolatile solids that are poorly soluble in organic solvents, but soluble in water and common alcohols.

<span class="mw-page-title-main">Phosphite ester</span> Organic compound with the formula P(OR)3

In organic chemistry, a phosphite ester or organophosphite usually refers to an organophosphorous compound with the formula P(OR)3. They can be considered as esters of an unobserved tautomer phosphorous acid, H3PO3, with the simplest example being trimethylphosphite, P(OCH3)3. Some phosphites can be considered esters of the dominant tautomer of phosphorous acid (HP(O)(OH)2). The simplest representative is dimethylphosphite with the formula HP(O)(OCH3)2. Both classes of phosphites are usually colorless liquids.

Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.

<span class="mw-page-title-main">Thiophosphoryl chloride</span> Chemical compound

Thiophosphoryl chloride is an inorganic compound with the chemical formula PSCl3. It is a colorless pungent smelling liquid that fumes in air. It is synthesized from phosphorus chloride and used to thiophosphorylate organic compounds, such as to produce insecticides.

<span class="mw-page-title-main">Triethyl phosphite</span> Chemical compound

Triethyl phosphite is an organophosphorus compound, specifically a phosphite ester, with the formula P(OCH2CH3)3, often abbreviated P(OEt)3. It is a colorless, malodorous liquid. It is used as a ligand in organometallic chemistry and as a reagent in organic synthesis.

<span class="mw-page-title-main">Trimethyl phosphite</span> Chemical compound

Trimethyl phosphite is an organophosphorus compound with the formula P(OCH3)3, often abbreviated P(OMe)3. It is a colorless liquid with a highly pungent odor. It is the simplest phosphite ester and finds used as a ligand in organometallic chemistry and as a reagent in organic synthesis. The molecule features a pyramidal phosphorus(III) center bound to three methoxy groups.

<span class="mw-page-title-main">Chlorodiphenylphosphine</span> Chemical compound

Chlorodiphenylphosphine is an organophosphorus compound with the formula (C6H5)2PCl, abbreviated Ph2PCl. It is a colourless oily liquid with a pungent odor that is often described as being garlic-like and detectable even in the ppb range. It is useful reagent for introducing the Ph2P group into molecules, which includes many ligands. Like other halophosphines, Ph2PCl is reactive with many nucleophiles such as water and easily oxidized even by air.

In organophosphorus chemistry, the Kabachnik–Fields reaction is a three-component organic reaction forming α-aminomethylphosphonates from an amine, a carbonyl compound, and a dialkyl phosphonate, (RO)2P(O)H (that are also called dialkylphosphites). Aminophosphonates are synthetic targets of some importance as phosphorus analogues of α-amino acids (a bioisostere). This multicomponent reaction was independently discovered by Martin Kabachnik and Ellis K. Fields in 1952. The reaction is very similar to the two-component Pudovik reaction, which involves condensation of the phosphite and a preformed imine.

<span class="mw-page-title-main">Diethyl phosphorochloridate</span> Chemical compound

Diethyl chlorophosphate is an organophosphorus compound with the formula (C2H5O)2P(O)Cl. As a reagent in organic synthesis, it is used to convert alcohols to the corresponding diethylphosphate esters. It is a colorless liquid with a fruity odor. It is a corrosive, and as a cholinesterase inhibitor, highly toxic through dermal absorption. The molecule is tetrahedral.

<span class="mw-page-title-main">Diphenylphosphine oxide</span> Chemical compound

Diphenylphosphine oxide is an organophosphorus compound with the formula (C6H5)2P(O)H. It is a white solid that soluble in polar organic solvents.

<span class="mw-page-title-main">Dimethylphosphine oxide</span> Chemical compound

Dimethylphosphine oxide is an organophosphorus compound with the formula (CH3)2P(O)H. It is a colorless liquid that soluble in polar organic solvents. It exists as the phosphine oxide, not the hydroxy tautomer. A related compound is diphenylphosphine oxide. Both are sometimes called secondary phosphine oxides.

<span class="mw-page-title-main">Dimethylphosphite</span> Chemical compound

Dimethylphosphite is an organophosphorus compound with the formula (CH3O)2P(O)H, known as dimethyl hydrogen phosphite (DMHP). Dimethylphosphite, is a minor tautomer of the phosphorus(V) derivative. It is a reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. The molecule is tetrahedral. It is a colorless liquid. The compounds can be prepared by methanolysis of phosphorus trichloride or by heating diethylphosphite in methanol.

In organophosphorus chemistry, an aminophosphine is a compound with the formula R3−nP(NR2)n where R = H or an organic substituent, and n = 0, 1, 2. At one extreme, the parent H2PNH2 is lightly studied and fragile, but at the other extreme tris(dimethylamino)phosphine (P(NMe2)3) is commonly available. Intermediate members are known, such as Ph2PN(H)Ph. These compounds are typically colorless and reactive toward oxygen. They have pyramidal geometry at phosphorus.

In chemistry hydrophosphonylation refers to any reaction where addition across a double bond generates a phosphonate (RP(O)(OR')2) group. Examples include the Kabachnik–Fields reaction, where a dialkylphosphite reacts across an imine to form an aminophosphonate. The reaction is catalyzed by bases and is subject to organocatalysis. Important compounds generated by this reaction include the common herbicide glyphosate.

References

  1. 1 2 Green, Kenneth (2001). "Diethyl Phosphonite". Encyclopedia of Reagents for Organic Synthesis . doi:10.1002/047084289X.rd211. ISBN   0471936235.
  2. 1 2 Malowan, J. E. (1953). "Diethyl Phosphite". Inorganic Syntheses. Vol. 4. pp. 58–60. doi:10.1002/9780470132357.ch19. ISBN   9780470132357.{{cite book}}: |journal= ignored (help)
  3. ↑ Ford-Moore, A. H.; Perry, B. J. (1951). "Triethyl Phosphite". Org. Synth. 31: 111. doi:10.15227/orgsyn.031.0111.
  4. ↑ Pedrosa, Leandro (March 20, 2011). "Esterification of Phosphorus Trichloride with Alcohols; Diisopropyl phosphonate". ChemSpider Synthetic Pages . Royal Society of Chemistry. SyntheticPage 488. doi: 10.1039/SP488 . Retrieved July 10, 2017.
  5. ↑ Fakhraian, H.; Mirzaei, A. (2004). "Reconsideration of the Base-Free Batch-Wise Esterification of Phosphorus Trichloride with Alcohols". Org. Process Res. Dev. 8 (3): 401–404. doi:10.1021/op049958v.
  6. ↑ Doak, G. O.; Freedman, Leon D. (1961). "The Structure and Properties of the Dialkyl Phosphonates". Chem. Rev. 61 (1): 31–44. doi:10.1021/cr60209a002.
  7. ↑ Guthrie, J. Peter (1979). "Tautomerization Equilibria for Phosphorous Acid and its Ethyl Esters, Free Energies of Formation of Phosphorous and Phosphonic Acids and their Ethyl Esters, and p Ka Values for Ionization of the P—H Bond in Phosphonic Acid and Phosphonic Esters". Canadian Journal of Chemistry. 57 (2): 236–239. doi: 10.1139/v79-039 .
  8. ↑ Malowan, John E. (1953). "Dioctyl Phosphite". Inorganic Syntheses. Vol. 4. pp. 61–62. doi:10.1002/9780470132357.ch20. ISBN   9780470132357.{{cite book}}: |journal= ignored (help)
  9. ↑ John M. Read, Yu-Pu Wang, Rick L. Danheiser (2015). "Synthesis of Phosphoryl Ynamides by Copper-Catalyzed Alkynylation of Phosphoramidates. Preparation of Diethyl Benzyl(oct-1-yn-1-yl)phosphoramidate". Org. Synth. 92: 156. doi: 10.15227/orgsyn.092.0156 .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ↑ Boeckman, Robert K.; Perni, Robert B.; Macdonald, James E.; Thomas, Anthony J. (1988). "6-Diethylphosphonomethyl-2,2-dimethyl-1,3-dioxen-4-one (Phosphonic acid, [(2,2-dimethyl-4-oxo-4H-1,3-dioxin-6-yl)methyl]-, diethyl ester)". Organic Syntheses . 66: 194. doi:10.15227/orgsyn.066.0194.; Collective Volume, vol. 8, p. 192
  11. ↑ Hays, Hugh R. (1968). "Reaction of diethyl phosphonate with methyl and ethyl Grignard reagents". J. Org. Chem. 33 (10): 3690–3694. doi:10.1021/jo01274a003.
  12. ↑ Busacca, Carl A.; Lorenz, Jon C.; Sabila, Paul; Haddad, Nizar; Senanyake, Chris H. (2007). "Synthesis of Electron-Deficient Secondary Phosphine Oxides and Secondary Phosphines: Bis[3,5-bis(trifluoromethyl)phenyl]phosphine Oxide and Bis[3,5-bis(trifluoromethyl)phenyl]phosphine". Organic Syntheses . 84: 242. doi:10.15227/orgsyn.084.0242.
  13. ↑ Keglevich, György; Bálint, Erika (1 November 2012). "The Kabachnik–Fields Reaction: Mechanism and Synthetic Use". Molecules. 17 (11): 12821–12835. doi: 10.3390/molecules171112821 . PMC   6268146 . PMID   23117425. Open Access logo PLoS transparent.svg
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