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.
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]
Diethyl phosphite undergoes deprotonation with potassium tert-butoxide. This reactivity allows alkylation at phosphorus:[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:
^ abMalowan, J. E. (1953). Diethyl Phosphite. pp. 58–60. doi:10.1002/9780470132357.ch19. ISBN9780470132357. {{cite book}}: |journal= ignored (help)
^Ford-Moore, A. H.; Perry, B. J. (1951). "Triethyl Phosphite". Org. Synth. 31: 111. doi:10.15227/orgsyn.031.0111.
^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.
^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.
^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.
^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.
^Malowan, John E. (1953). "Dioctyl phosphite". Inorganic Syntheses. pp. 61–62. doi:10.1002/9780470132357.ch20. ISBN9780470132357. {{cite book}}: |journal= ignored (help)
^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)
^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
^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.
^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.
^Keglevich, György; Bálint, Erika (1 November 2012). "The Kabachnik–Fields Reaction: Mechanism and Synthetic Use". Molecules. 17 (11): 12821–12835. doi:10.3390/molecules171112821. PMC6268146. PMID 23117425.
August 21, 2023
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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 Diethylphosphite NamesPreferred IUPAC name Diethyl phosphonateOther names diethyl phosphonite DEP Phosphonic acid diethyl esterIdentifiersCAS Number 762 04 9 Y3D model JSmol Interactive imageBeilstein Reference 4 01 00 01329ChemSpider 12437ECHA InfoCard 100 010 992PubChem CID 12977UNII U9X9YBA22W YCompTox Dashboard EPA DTXSID9041861InChI InChI 1S C4H11O3P c1 3 6 8 5 7 4 2 h5H 3 4H2 1 2H3Key SULWMEGSVQCTSK UHFFFAOYSA NSMILES CCOP O OCCPropertiesChemical formula C 4H 11O 3PMolar mass 138 103 g mol 1Appearance colorless liquidDensity 1 072 g cm3Boiling point 50 51 C at 2 mm HgExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Infobox references Contents 1 Synthesis and properties 2 Reactions 2 1 Hydrolysis and alcoholysis 2 2 P alkylation 2 3 Hydrophosphonylation 3 See also 4 ReferencesSynthesis and properties EditThe 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 C2H5ClUnder 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 EditHydrolysis and alcoholysis Edit 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 C2H5OHSimilarly amines can displace ethoxide 9 C2H5O 2P O H RNH2 C2H5O RN H P O H C2H5OHP alkylation Edit Diethyl phosphite undergoes deprotonation with potassium tert butoxide This reactivity allows alkylation at phosphorus 10 C2H5O 2P O H KOtBu C2H5O 2P O K HOtBu C2H5O 2P O K RBr C2H5O 2P O R KBrFor 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 Edit 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 RIt can also add to imines in the Pudovik reaction and Kabachnik Fields reaction 13 in both cases forming aminophosphonatesSee also EditDimethyl phosphite Diisopropyl phosphite Diphenyl phosphiteReferences Edit a b Green Kenneth 2001 Diethyl Phosphonite Encyclopedia of Reagents for Organic Synthesis doi 10 1002 047084289X rd211 ISBN 0471936235 a b Malowan J E 1953 Diethyl Phosphite pp 58 60 doi 10 1002 9780470132357 ch19 ISBN 9780470132357 a href Template Cite book html title Template Cite book cite book a journal ignored help Ford Moore A H Perry B J 1951 Triethyl Phosphite Org Synth 31 111 doi 10 15227 orgsyn 031 0111 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 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 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 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 Malowan John E 1953 Dioctyl phosphite Inorganic Syntheses pp 61 62 doi 10 1002 9780470132357 ch20 ISBN 9780470132357 a href Template Cite book html title Template Cite book cite book a journal ignored help 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 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link 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 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 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 Keglevich Gyorgy Balint 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 Retrieved from https en wikipedia org w index php title Diethylphosphite amp oldid 1170161871, wikipedia, wiki, book, books, library,
