Dialkyl vinylphosphonate synthesis

Dialkyl vinylphosphonates.13 Pd(0) catalyzes the reaction of vinyl bromides and dialkyl phosphites in the presence of trielhylamine (1 equivalent) to form dialkyl vinylphosphonates. The configuration of the starting material is retained. An example is the synthesis of phosphonomycin (1, equation I). 

Aboujaoude, E.E., Lietje, S., Collignon, N., Teulade, M.P., and Savignac, P, A one step generation of a-lithio(trimethylsilyl)alkanephosphonates. A new preparative route to dialkyl l-(trimethylsi-lyl)alkanephosphonates and vinylphosphonates. Synthesis, 934, 1986. 

The most attractive and potentially most general route for the synthesis of dialkyl 1,2-epoxyalkylphosphonates appears to be the direct epoxidation of the corresponding dialkyl vinylphosphonates (Scheme 4.13). The syntheses of dialkyl vinylphosphonates with essentially any desired combination of a and 3 substituents can be achieved readily by a number of procedures. The use of vinylphosphonates offers appreciable advantages. The cis- and /ran.v-vinylphosphonates (R- or R ... 

The palladium-catalyzed phosphonylation was successfully applied to stereoselective synthesis of dialkyl vinylphosphonates from vinyl bromides and dialkyl H-phosphonates [368]. 

Arbuzov and Michaelis-Becker reactions provide facile and versatile procedures for the formation of carbon-phosphorus bonds. These methods, however, are not applicable to the formation of sp hybridized carbon-phosphorus bonds. Only few methods have been reported for the syntheses of arylphosphonates and vinylphospho-nates. Direct reaction of aryl or vinyl halides with trialkyl phosphite in the presence of nickel halide requires severe reaction conditions [21,22], and the stereochemistry of vinylphosphonates has not been clarified. Synthesis of dialkyl arylphosphonates 22 [23, 24] is achieved by the palladium-catalyzed reaction (Scheme 2.12), which is called by Hirao reaction . The stereoselective synthesis of dialkyl vinylphosphonates 23 [24-26] is similarly accomplished by this method (Scheme 2.13). A variety of modified procedures have been developed recently [27-37]. 

Because heteroatom-substituted vinylphosphonates such as enol phosphates and vinyl halides are masked acetylenic compounds, a variety of methods have been developed for their elaboration and subsequent use in the synthesis of dialkyl 1-alkynylphosphonates. These eliminations usually have the leaving group P to the phosphoryl group, although cases in which the leaving group is a to the phosphorus center are also known (Scheme 1.12). 

A report of the synthesis of thermodynamically stable ( )-vinylphosphonates from diethyl 1-formyl-l-phenylalkylphosphonates by a Homer-Wadswoilh-Ermnons-type reaction has appeared. Sodium P-hydroxyphosphonates, generated by the reaction of sodium dialkyl phosphites with... 

The Pd-catalyzed hydrophosphonylation of terminal alkynes with dialkyl phospliites seems destined to become the method of choice for tlie synthesis of a-substituted vinylphosphonates. The reaction proceeds by regioselective attack of dialkyl phosphite at the internal carbon of the triple bond (Scheme 6.37). Thus, 5-cyano-l-pentyne reacts efficiently with dimethyl phosphite in the presence of cZv-PdMe2(PPh2Me)2 affording dimethyl l-(3-cyanopropyl)vinylphosphonate in 94% yield. In the absence of catalyst, the hydrophosphonylation product is not detected. ... 

An imine-enamine annulation has been used in the synthesis of the indoloquinolizidine alkaloid ( )-deplancheine.52 The annulation of dialkyl (1-alkoxycarbonyl)vinylphosphonates via a Horner-Wadsworth-Emmons reaction has been developed in the synthesis of [3.3.0] fused pyrazolid-inones from monocyclic pyrazolidinones. - Treannent of diethyl l-(ethoxycarbonyl)vinylphos-phonate in excess (2 eq) with imide anions such as phthalimide, maleimide, and succinimide successfully produces the corresponding six-membered fused heterocycles. Similarly, synthesis of functionalized cyclohexenylphosphonates is achieved by condensation of diethyl l-(ethoxycar-bonyl)vinylphosphonate (2 eq) with cyclopentanone enolates (Scheme 8.29). - ... 

Two Pd(0)-catalyzed coupling reactions are reported for the synthesis of dialkyl 2-(ethoxycar-bonyl)vinylphosphonates. Thus, alkenyl triflates in DMF at room temperature and p-bromo acrylates in toluene at 80°C undergo very facile and efficient Pd(PPh3)4-catalyzed coupling with dialkyl phosphites to provide alkenyl phosphonates in high isolated yields (87-90%, Scheme 8.52). ... 

Phosphonate carbanions (97), generated by the addition of various carbanions to vinylphosphonates, provide routes to functionalized alkenes. Thermolysis of the dienes (98) prepared in this way offers a route to 1,4-disubstituted benzenes via electrocyclization of the intermediate trienes (99) (Scheme 17). The reaction of phosphonate carbanion (100) with alkyl or aryl benzenethiosulphonates provides a general synthesis of the useful dialkyl alkyl- and aryl-thiomethyl-phosphonates (101). ... 

Scheme 6.12 Synthesis of 0,0-dialkyl 1-(substituted phenoxy acetoxy)vinylphosphonates M25...

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