Alkynylphosphonic acids

Two procedures for the transformation of diesters of 1-alkynylphosphonic acids into monoesters have been described. They involve the selective replacement of one ethoxy group by chlorine... 

Tarasov, V.V.. Arbisman, Y.S., Kondrat ev, Y.A., and Ivin, S.Z., Investigations in the series of phosphorus-containing compounds with acetylene and allene groupings. Part 3. Infrared spectra of some derivatives of substituted alkynylphosphonic acids, Zh. Obshch. Khim., 38, 130, 1968 J, Gen, Chem. USSR (Engl. Transl.), 38, 129, 1968. 

Alkenyl, Alkynyl, Aryl and Related Acids. Vinylphosphonates are an important group of compounds that have found use in organic transformations. They are also useful reagents for the synthesis of biologically active systems. The synthesis of vinylphosphonates is varied. However additional convenient routes to them are always welcome. Four recent reports demonstrated that zirco-nacycles (180), readily available from diethyl 1-alkynylphosphonates, are very useful precursors of different vinylphosphonates. They react with alkynes, aldehydes, ketones acyl chlorides and nitriles to produce, in a highly stereo- and regio-selective manner, substituted vinylphosphonates (181), (182), (183) (184) and (185) respectively (Scheme 46). 

Two variants of this rearrangement have been reported. One uses triethyl phosphite instead of diethyl chlorophosphite. Thus, in the presence of a catalytic amount of para-toluenesulfonic acid, triethyl phosphite reacts with propargyl alcohol in DMF at room temperature to give a mixture of diethyl allenylphosphonate (51%) and diethyl 1-propynylphosphonate (14%). The second variant is based on the conversion of dialkyl allenylphosphonates (R , R H, R = H, Scheme 1.19) into dialkyl 1-alkynylphosphonates by a photochemically allowed [l,3s]-sigmatropic shift in ( ,11, with 46-50% yields. ... 

The cycloaddition of 1-pyrrolidylcyclopentene with activated alkynes, such as dimethyl acctylcne-dicarboxylate, is reported to occur at room temperature. In contrast, the less reactive diethyl 1-alkynylphosphonates require reaction temperatures of at least 85°C to permit cycloaddition. Under such conditions, spontaneous ring opening of the thermally unstable cyclobutene intermediate yields the ring-enlarged product. Acid hydrolysis of the product enamine gives the unsaturated P-keto-phosphonate (Scheme 1.22). The best results for the cycloaddition are obtained with rigorous exclusion of moisture and with temperatures held below 100°C. Reaction times varied from 24 h (Rl = H) to 8 days (Ri = MOM). -... 

Bromo- and iodotrimethylsilane, reagents compatible with alkyne and other functionalities, are suitable for the mild P-0 dealkylation of dialkyl 1-alkynylphosphonates to give the corresponding phosphonic acids.The greater reactivity of iodotrimethylsilane will probably prove advantageous for the low-temperature dealkylation of phosphonates having triple bonds. However, transesterification of diethyl 2-propynylphosphonate with iodotrimethylsilane at -30°C followed by solvolysis with MeOH led quantitatively to the 1-propynylphosphonic icid. ... 

Synthesis of phosphonic acids and their derivatives An efficient and remarkably clean practical procedure for allqmylation of dialkyl phosphites with readily available, bench-stable copper acetylides (314) has been reported by Evano et In the presence of iV-methyli-midazole (NMI) as a ligand, corresponding alkynylphosphonates (315) have been readily obtained in good to excellent yields at room temperature and in a multigram scale (Scheme 85). 

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