Vinylphosphonates addition reactions

Several addition reactions of mono- and di-enephosphonates have been reported. Diethyl vinylphosphonate reacts at 100 °C with cyclohexanone pyrrolidenamine in a stepwise fashion. Hydrolysis of the initial adduct yields the ketophosphonate (143) but further reaction of the adduct in a Mannich-type process can yield, ultimately, the cyclobutenylphosphonate (144).112 Diethyl butadienephosphonate condenses... 

Several addition reactions of unsaturated phosphonic and phosphinic esters have been reported during the course of the year. Dithiophosphoric acids add to 2-alkoxy-vinylphosphine esters in the expected manner, and in the addition of phenyl azide to vinylphosphonates, the initial triazole (95) may be thermolysed to a C-phosphory-lated aziridine, but in the presence of triethylamine the final products are 2-anilino-vinylphosphonates. ... 

A number of addition reactions have been reported. For example, diethyl vinylphosphonate reacts with the enolates of cyclohexanone and 2-methylcyclohexanone, generated in situ by the treatment of silyl enol ethers with benzyltrimethylammonium fluoride, to give the corresponding Michael adducts in 31% and 44% yields, respectively. ... 

Reductive Addition. Radical addition to activated olefins with alkyl bromides to form a carbon-carbon bond can be also carried out in the presence of TPDS initiated by AIBN in ethanol. Other activated olefins such as diethyl vinylphosphonate and ethyl acrylate can be also used in the addition reaction. The reductive addition of 1-bromoadamantane to diethyl vinylphosphonate with TPDS initiated by AIBN to form the corresponding diethyl 2(l-adamantyl)ethylphosphonate in good yield is shown in eq 4. 

The addition reaction with other alkyl bromides and xanthates to activated olefins such as phenyl vinyl sulfone and diethyl vinylphosphonate, with TPDS-AIBN, also gives the corresponding reductive addition products in moderate to good yields (40-84%). Unfortunately, reductive addition of chalcogenides to activated olefin with the TPDS-AIBN method does not work effectively due to the lower reactivity of chalcogenides toward the... 

The synthetic potential of the obtained phosphonates has been demonstrated in electron-deficient iminophosphonates by their easy functionalisation to afford various acyclic and heterocyclic derivatives with an aminophosphonic fragment by the use of reductive nucleophilic addition reactions, direct aminoallg lation of electron-rich heterocycles, cyclocondensations, and dipolar cycloaddition reactions. In the subsubsection devoted to reactions of phosphonates, ketophosphonates, vinylphosphonates, alkinylphosphonates, vinyl- and vinylidenebisphos-phonates were widely used as organophosphorus reagents. 

Tanaka et al. were the pioneers of the synthetic application of catalytic hydrophosphorylations and hydrophosphinylations of multiple carbon-carbon bonds. Addition to alkynes was catalyzed by Pd complexes and led to vinyl-phosphonates in high yields under relatively mild conditions (Scheme 8.2) [66]. In some cases an excellent a-regioselectivity was reported. As an exception, trimethylsilylacetylene gave trans-jS-trimethylsilyl-vinylphosphonate in the addition reaction presumably due to steric hindrance. Various a-substituted vinylphospho-nates were synthesized from terminal alkynes in 80-95% yield and 92-96% regioselectivity using c -PdMe2(PPh2Me)2 as the catalyst precursor. 

Tetrasubstituted allene 2,4-diethyl-2,3-pentadiene was also reacted with H-phosphonate, but the addition reaction was accompanied with double bond isomerization leading to a mixture of allyl- and vinylphosphonates. 

Fluoroalkanephosphonic acid can be obtained by addition of iodine perfluoroalkane to vinylphosphonic acid dichloride followed by saponification and deiodination by sodium amalgam [141]. Fluoroalkanephosphonic acids can be transformed to fluoroalkanephosphonic acid glycil esters by 2 mol of epi-chlorhydrin in a water-free solution followed by reaction with alkalines or amines [142]. Compounds of this kind with an alkyl chain of 8-20 carbon at-... 

The optically active a-sulfinyl vinylphosphonate 122 prepared in two different ways (Scheme 38) is an interesting reagent for asymmetric synthesis [80]. This substrate is an asymmetric dienophile and Michael acceptor [80a]. In the Diels-Alder reaction with cyclopentadiene leading to 123, the endo/exo selectivity and the asymmetry induced by the sulfinyl group have been examined in various experimental conditions. The influence of Lewis acid catalysts (which also increase the dienophilic reactivity) appears to be important. The 1,4-addition of ethanethiol gives 124 with a moderate diastereoselectivity. 

Diazoalkanes add readily to the double bond of esters of vinylphosphonic acid, giving the pyrazoline derivatives (100), which can lose nitrogen to give esters of cyclopropylphosphonic acids. In a similar reaction, acyl-phosphonic acid esters (101) were converted to epoxy-derivatives (102). A -Phenylsydnone adds to diethyl prop-l-ynephosphonate, giving the pyra-zole (103). The addition of cyclopentadiene to dimethyl vinyl phosphate leads to an exojendo quotient of 1.2, but with hexachlorocyclopentadiene only e/ii/o-isomer is formed. ... 

A-trityl-(l/ ,2S)-norephedrine (58), the corresponding allyl phosphonates 62a,b were obtained via the Arbusov rearrangement of 2-ethoxy-1,3,2-oxazaphospholidine 60. The absolute configuration of the major diastereomer, 62a was determined by X-ray as (2S1,45,51 ).The reaction of the major diastereomer of allyl phosphonates 61a and 62a with DBU afforded the corresponding vinylphosphonates 63a,b (Scheme 21) [48], Nucleophilic addition to these resulted in induction of chirality at the [1-position of the stereogenic phosphorus atom in the initially produced diastereomeric phosphonates 64 or 65 (Scheme 21) [48],... 

Carbocyclization of m-alkcnyl-z-methoxybcnzy I lithiums to form five- or six-membered rings has been studied 101 the five-membered ring is formed with a cis-stereochemical relationship between the methoxy substituent and the adjacent methyl group. Intramolecular carbolithiation of vinyl sulfides at — 105°C in THF has been found to occur non-stereospecifically with regard to the newly formed C—Li centre.102. The stereochemistry of selective tandem Michael addition alkylation reactions of vinylphosphonates has been explored.103... 

The conjugated addition of the lithiated bis-lactim ether derived from cyclo-[Gly-D-Val] (263) to a-substituted vinylphosphonates (264) or electrophilic substitution on the lithiated bis-lactim ether derived from cyc/o-[L-AP4-D-Val] (265) take place regio- and stereoselectively. These reactions allow direct access... 

A new route to p-keto phosphonates (141) and (142) from diethyl 1-(trimethylsilyl)vinylphosphonate (140) has been reported.Reaction of (140) with lithium alkyls followed by addition of acid chloride or alkyl isocyanates provides (141) or (142), respectively (Scheme 28). a,P-... 

The Baylis-Hillman reaction has become a very powerful carbon-carbon bond forming reaction in the past 20 years. A typical reaction involves an activated olefin (i.e., an acrylate) and an aldehyde in the presence of a tertiary amine such as diazobicyclo-[2.2.2]octane (DABCO) to form an a-meihylhydroxyacrylale. A host of activated olefins have been utilized including acrylates, acroleins, a, 3-unsaturated ketones, vinylsulfones, vinylphosphonates, vinyl nitriles, etc. The Baylis-Hillman has been successfully applied inter- and intramolecularly. In addition, there are numerous examples of asymmetric Baylis-Hilhnan reactions. Reviews (a) Ciganek, E. Org. React. 1997, 51, 201-478. (b) Basavaiah, D. Rao, P. D. Hyma, R. S. Tetrahedron 1996, 52, 8001-8062. (c) Fort, Y. Berthe, M. C. Caubere, P. Tetrahedron 1992, 48, 6371-6384. 

A vai iety of diethyl vinylphosphonates have been oxidized in moderate to good yields (19-84%) using dioxirane generated in situ from buffered monopersulfate (Oxone ) and a ketone in a two-phase (ClECb/lEO) reaction mixture.Because of the pH dependence of dioxirane stability, the process needs an accurate control of the pH at 7.4. However, the reaction is often very sluggish and requires regular addition of fresh portions of oxone and lengthy reaction times. 

Disappointing results have been obtained from the Michael addition of compounds containing active methylene groups to vinylphosphonates. For example, cyanoacetate reacts with the diethyl vinyphosphonate under the conditions of base catalysis to give a mixture of 1 1 and 1 2 adduct resulting of one or two additions to the vinylphosphonate. When 2-pyridylacetonitrile and cyanomethylphosphonate are subjected to this reaction, diethyl 3-(2-pyridyl)- or 3-diethoxy-phosphinyl-3-cyanopropylphosphonates are obtained in 61% and 98% yields, respectively (Scheme 6.35). 

Pudovik, A.N., and Grishina. O.N., Synthesis and properties of vinylphosphonic esters. Part 2. Phosphonoethylation reaction. Addition of malonic, cyanoacetic, acetoacetic ester, and their homo logs to vinylphosphonic ester. Zh. Obshch. Khim., 23, 267, 1953 Chem. Abstr, 48, 2573c, 1954. 

The sodium salts of dialkyl l-(alkoxycarbonyl)methylphosphonates. in the presence of a further equivalent of NaH, undergo addition of carbon disulfide in EtjO at room temperature to give alkenedithiolates, which are characterized by protonation, alkylation (Mel, EtI, BnCl), oxidation, and phosgenation. For example, reaction with metliyl iodide provides the dialkyl 1-alkoxycarbonyl-2,2-/7i.v(mcthylthio)vinylphosphonates in good yields (68-75%), whereas room-temperature treatment with acetyl or benzoyl clilonde produces l,3-dithietane-2,4-diylidene-foZ5 [(alkoxycarbo-nyl)methylphosphonates] in moderate yields (18-39%, Scheme 8.23). The same oxidation product is obtained by reaction with iodine. 

The use of diethyl l-(ethoxycarbonyl)vinylphosphonate is based on Michael addition of anionic nucleophiles to the double bond to produce stabilized phosphonate anions capable of undergoing subsequent alkenylation reaction with aldehydes or ketones by a Homer-Wadsworth-Emmons process (Scheme 8.27)." 2 " "... 

Oxygen and nitrogen nucleophiles add to diethyl l-(ethoxycarbonyl)vinylphosphonate to generate the formation of various fused heterocyclic compounds. Thus, A -carbapcncrns are readily prepared by the Michael addition of A-lithio-4-vinylazetidin-2-one to diethyl l-(ethoxycarbo-nyl)vinylphosphonate followed by ozonolysis of the adduct and subsequent treatment of the generated aldehyde by intramolecular Homer Wadsworth-Emmons reaction (Scheme 8.28). ... 

In Michael-type reactions, unsaturated phosphorus substrates such as dimethyl vinylphosphonate and tetraethyl ethenylidenediphosphonate undergo addition of carbanions from ethyl... 

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