【English name】Diethyl Phosphonate
[Molecular formula] C4H11O3P
【Molecular weight】138.10
[CA registration number][762-04-9]
[Abbreviation and alias] DEP
【Structural Formula】HP(O)(OEt)2
[Physical properties] Colorless liquid, bp 50~51 oC/2.0mmHg, d 1.072 g/cm3. It is soluble in water, tetrahydrofuran and ethanol.
【Preparation and Commercial Products】This reagent can be prepared by direct reaction of phosphorus trichloride and excess ethanol.
【Note】This reagent is sensitive to moisture and needs to be filtered to remove suspended solids before use.
Nucleophilic substitution reaction
Under the action of a strong base, DEP can form negative ions, which can undergo nucleophilic substitution reactions with halogenated compounds (such as those made from alcohols). A variety of phosphonates (Formula 1)[1~4] can be synthesized using this method.
Synthesis of palladium-catalyzed phosphonates
Under the catalysis of transition metal complexes [such as Pd(PPh3)2, Pd(PPh3)4], DEP can catalyze halogenated aromatic compounds [5~7], halogenated alkenes [8,9], and alkynes [ 10] reacts to form phosphonate ester. During the reaction, palladium is inserted into the middle of the carbon-halogen bond and forms a complex with phosphorus, and then the phosphorus is transferred to the carbon to form a phosphonate ester (formula 2) [5].
Nucleophilic addition reaction with unsaturated bonds
In the presence of a strong base, the negative ions formed by DEP can undergo nucleophilic addition reactions with unsaturated bonds such as aldehydes (formula 3) [11,12] and imines [13,14] to obtain phosphonate esters compounds. It should be noted that both reaction rate and reaction yield are affected by steric hindrance. Some of these reactions [13,14] can achieve good stereoselectivity under the induction of chiral ortho groups.
Free radical addition reaction with unsaturated bonds
In the presence of free radical initiators, DEP can also react with unsaturated compounds such as imines (Formula 5) [17] to obtain phosphonate esters.
Todd’s reaction
In the presence of CCl4 and N(Et)3, DEP can react with amines to form amine phosphate (Formula 6) [18]. This reaction can be carried out in the aqueous phase. The reaction proceeds through the formation of a P-Cl bond intermediate, followed by the attack of the amine as a nucleophile on the phosphorus atom.
