Alkenyl phosphonates, synthesis

Ohler, E., Zbiral, E., and El-Badawi, M., A novel and versatile synthesis of heterocyclic aldehydes using dialkyl 3-oxo-l-alkenyl-phosphonates, Tetrahedron Lett., 24, 5599, 1983. 

Ohler, E., and Kotzinger, S., Synthesis of (3-amino-l-alkenyl)phosphonic acids from allylic a- and y-hydroxyphosphonates. Sigmatropic reanangement of dialkyl (l-azido-2-alkenyl)phosphonates, Liebigs Ann. Chem., 269, 1993. 

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). ... 

Srebnik has reported the synthesis of phosphono boronates by hydroboration with pinacol borane (30) [92]. The reaction proceeds well with terminal alkenyl phosphonates whereas internal alkenyl phosphonates gave complex mixtures. Hydroboration of the corresponding alkynyl phosphonates under identical conditions gave alkenyl phosphonates that were difficult to isolate and were in situ subjected to Suzuki coupling with phenyl iodide to give trisubstituted phosphonates providing a new one-pot synthesis of this class of compounds (Scheme 3.60). 

Lazrek HB, Rochdi A, Khaider H, Barascut J-L, Imbach J-L, Balzarini J, Witvrouw M, Pannecouque C, De Clercq E (1998) Synthesis of (Z) and ( ) a-Alkenyl phosphonic acid derivatives of purines and pyrimidines. Tetrahedron 54 3807-3816... 

Ohler E, Kotzinger S (1993) Thermal rearrangement of trichloroacetimidic esters of allylic a-hydroxyphosphonates a convenient way to (3-amino-l-alkenyl)phosphonic acids. Synthesis 497-502... 

The ring opening of activated azetidin-2-one 317 by a phosphonate-stabilized carbanion yielded the /3-ketophos-phonate 318 (Equation 109) <2002TL9641>. The Horner-Wadsworth-Emmons alkenylation and subsequent reduction of the latter compound affords a /3-aminoketone, which is used in the synthesis of sphingosine and phytosphingos i ne. 

Ohler, E., and Zbiral, Ii., Reaction of dialkyl phosphites with a-enones. Part 1. Synthesis and allylic reanangement of dimethyl (l-hydroxy-2-alkenyl)- and (l-hydroxy-2-cycloalkenyl)phosphonates, Chem. Ber.. 124, 175, 1991. 

Phosphonates (10) and phosphine oxides (11) were prepared for use in the synthesis of a series of new alk-l-enyl derivatives of adenine and thymidine (Scheme 4) via Horner reactions and Horner-Wadsworth-Emmons reactions on carbonyls. This approach, complementary to the previously reported methods for the preparation of iV-(alk-l-enyl) nucleobases, offers a novel general strategy to access trisubstituted alkenyl nucleobases. 

The reactions between PCI5 and alkenes or alkynes have already been discussed extensively in connection with the synthesis of a variety of phosphonic acid types (as their acid dichlorides). Successful applications have also used alkenyl alkyl sulphides (to give the dichlorides 381) to an enyne (to give the dichloride 382) and to RSC CCl (to give 383)584,585 variation of the Pummerer reaction consists in the interaction of PCI5 and a dialkyl sulphoxide, during which a trichlorophosphonium salt intermediate is decomposed with SO2 to yield a (2-alkylthioethenyl)phosphonic dichloride (Scheme 34). ... 

Coupling reactions of alkyl boranes, formed by hydroboration of alkenes, with unsaturated halides (or triflates or phosphonates) is possible, and this reaction is finding increasing use in synthesis. For example, coupling of the alkyl borane derived from hydroboration (with 9-borobicyclo[3.3.1]nonane, 9-BBN) of the alkene 200 with the alkenyl iodide 201 gave the substituted cyclopentene 202, used in a synthesis of prostaglandin Ei (1.205). This type of B-alkyl Suzuki coupling reaction is very useful for the synthesis of substituted alkenes. 

Pd-catalyzed arylation of various phosphorus compounds containing P—H bonds with aryl and alkenyl halides, or triflates offers useful methods of C— P bond formation. After pioneering work on Pd-catalyzed arylation and alkenylation of dialkyl phosphonates by Hirao etal., extensive studies have been carried out on arylation of various phosphorus compounds. The methods are particularly useful for the synthesis of various chiral phosphines used in Pd-catalyzed asymmetric reactions. 

Hirao et al. synthesized diethyl p-anisylphosphonate 61 by arylation of diethyl phosphonate (60) with p-bromoanisole (59) [1], The reaction was applied to the synthesis of the phosphonate 63a by coupling of the alkenyl bromide 62 with the phosphonate 63 [18],... 

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