P-hydroxyphosphonates

The reduetion of N-benzylamino-p-ketophosphonates with Zn(BH4)2 shows excellent levels of anti-stereoselectivity to give preferentially anti- a-benzylami-no-p-hydroxyphosphonates (354) (Figure 57). ... 

The mechanism of phosphonate anion (135) addition to carbonyl derivatives is similar to the phosphonium ylide addition however, there are several notable features to these anion additions that distinguish the reactions fix)m those of the classical Wittig. The addition of the anion gives a mixture of the erythro (136 and 137) and threo (139 and 140) isomeric p-hydroxyphosphonates (Scheme 24). In the case of phosphine oxides, the initial oxyanion intermediates may be trapped. The anion intermediates decompose by a syn elimination of phosphate or phosphinate to give the alkene. The elinunation is stereospecific, with tile erythro isomer producing the ci.r-alkene (138), and the threo addition adduct producing the... 

The (Z)-selectivity is presumed to occur because of rapid elimination of the P-hydroxyphosphonate before equilibration can take place. Several base and solvent combinations were explored, including triton B, K2CO3 and KOBu, but potassium hexamethyldisilazide with 18-crown-6 in THF gave the most... 

Alkenyl, Alkynyl, Aryl, Heteroaryl and Related Acids. - Alkenyl-phosphonates have been prepared by the dehydration of P-hydroxyphosphonates with DCC and CuCh, by dehydrohalogenation of P-bromoalkylphosphonates with triethyl orthoformate, and from alk-l-ynylphosphonates 116 by hydrogenation using Lindlar s catalyst (to give the m-isomer 118) and by stereoselective addition of alkylcuprates to give 117 (Scheme 7). A convenient... 

Heating diethyl 2-propenylphosphonate with Et.SiH in the presence of di-tert-butylperoxide at 140°C affords diethyl 3-(triethylsilyl)propylphosphonate in low yield (21%). Under the same conditions, diethyl 4-(triethylsilyl)butylphosphonate is prepared in 63% yield from diethyl phosphite and 4-(triethylsilyl)-l-butene. Addition of (trimethylsilyl)methylmagnesium chloride to diethyl l,l-difluoro-2-oxo-2-(tert-butoxycarbonyl)etliylphosphonate in THF at low temperature results in the formation of y-silylated P-hydroxyphosphonate in 65% yield. ... 

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... 

Sturtz, G., and Baboulene, M., a-Aminoalcohols. y-Amino-P-hydroxyphosphonates, Chim. Ther., 4, 195. 1969. 

Takaki, K., Itono, Y., Nagafuji, A., Naito. Y.. Shishido, T., Takehira, K., Makioka, Y, Taniguchi, Y, and Fujiwara, Y. Three-component coupling of acylphosphonates and two carbonyl compounds promoted by low-valent samariums. One-pot synthesis of P-hydroxyphosphonates, J. Org. Chem., 65, 475, 2000. 

A procedure for the transformation of a formyl moiety into p-ketophosphonate has been described. It involves the selective addition of dimethyl l-Uthiomethylphosphonate to the formyl group followed by oxidation with CrO,-Py of the intermediate P-hydroxyphosphonate. ... 

SCHEME 4.157 Iron-catalyzed synthesis of p-hydroxyphosphonates from alkenes [247],... 

The report on the synthesis of the phosphonate isostere of AZT 5 -phosphate by a BF3-Et20-catalyzed nucleophilic addition of diethyl methanephosphonate to an oxetane prompted us to apply the same reaction conditions to the opening of epoxides. Indeed, when the anion of the same phosphonate was generated with BuLi in THF, followed by the sequential addition of epoxide 10a or 10b and BF3-Et20 at -78°, the corresponding P-hydroxyphosphonates 20 (a and c) were obtained in quantitative yield.26 Extension of this reaction to a phosphorus nucleophile proved to be equally effective. Thus, when diethyl phosphite was condensed with the same epoxides under identical reaction conditions, the corresponding P-hydroxyphosphonates 20 (b and d) were isolated in... 

The synthesis and resolution of enantiomerically pure (R)- and (5)-p-hydroxyphosphonates (642a) and (642b) bearing adenine, as a nucleobase. 

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