Diethyl phosphonate 628 Subject

The reaction of a-bromo-a,p-unsaturated ketones with diethyl phosphonate and triethylamine affords p,y-unsaturated ketones selectively (Scheme 2.5) [15]. This process comprises reduction of the bromide and deconjugation of an olehnic moiety. a-Bromo-a,p-unsaturated carbonyl compounds are readily prepared by treatment of l,l-dibromo-2-siloxycyclopropanes with diethyl phosphonate. This finding makes it possible to prepare p.y-unsaturated ketones from l,l-dibromo-2-siloxycy-clopropanes in one pot. As one of the plausible reaction paths, the a-bromo-p,y-unsaturated ketone, arising from the intervention of the dienol, is subjected to debromination with diethyl phosphonate and triethylamine to give the p,y-unsaturated ketone. 

The synthetic P-o-glucopyranoside 30 was converted to the cyanoglucoside rho-diocyanoside A (38a), which was isolated from the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey. (Crassulaceae) and found to show antiallergic activity in a passive cutaneous anaphylaxis test in rat. Acetylation of 30 gave an acetate (98% yield) which was subjected to ozonolysis to afford the aldehyde 39. The Horner-Emmons reaction of 39 using diethyl (l-cyanoethyl)phosphonate furnished (Z)-40a (32% yield from 30) and ( )-40b (10% yield from 30). The physical... 

Chloroform reacts with triethyl phosphite in a peroxide-catalysed reaction that leads exclusively to the competing product diethyl ethylphosphonate.275 On the other hand, carbon tetrachloride and the same ester give a high yield of the expected (trichloromethyl)phosphonate if boiled in the absence of radical-formers276 or subjected to UV-irradiation in the cold.277... 

In the presence of piperidine in benzene, benzaldehyde reacts with diethyl (nitromethyl)-phosphonate to afford at 67% yield of diethyl (2-hydroxy-l-nitro-2-phenylethyl)phos-phonate, presumably as a mixture of diastereoisomers. However, a similar reaction with 4-nitrobenzaldehyde leads to phosphorus-carbon bond cleavage and the formation of 1-nitro-2-(4-nitrophenyl)ethane. The converse procedure, i.e. a reaction which involves a nitroalkane and an (oxoalkyl)phosphonic diester, is also subject to certain restrictions. The base-catalysed nucleophilic additions of nitromethane to dialkyl acetylphosphonates (Scheme 7 R = Me) to give dialkyl [(1-hydroxy-l-nitromethyl)alkyl]phosphonates have... 

In order to obtain examples of aminohydroxyalkyl phosphonic acids diastereoisomerically enriched at the hydroxy site, the aldehyde (196) (from L-phenylalanine) was subjected to reactions with phosphorus(III) nucleophiles (Scheme 21) with diethyl rcrf-butyidimethylsilylphosphite it gave the adducts (197) and (198) (X = Bn, Y = SiMe2Bu ), convertible conventionally into (197) and (198)(X = Bn, Y = H), and thence to (197) and (198)(X = Y = H). The diastereoisomeric composition of the mixture was determined through a conversion into the oxazolidin-2-ones (199). In this way it was found that the ratio of (197)/(198)(X = Y = H) was >98 <2, a degree of selectivity which... 

In a study of the flame retardance of styrene-methyl methacrylate copolymer with covalently bound pyrocatechol-vinyl phosphate, diethyl p-vinyl benzyl phosphonate, or di(2-phenyl ethyl phosphonate) groups. Ebdon and co-workers [23] obtained data on their decomposition behaviour. This was achieved by reducing the rate of liberation of flammable methyl methacrylate monomer during combustion. Possible mechanisms for these processes are suggested. Other methacrylate copolymers which have been the subject of thermal degradation studies include PMMA-N-methylmaleimide-styrene [24] and PMMA-ethylene vinyl acetate [25-27]. 

Phosphonylpyrazole 4 To a stirred solution of aldehyde (1 0.5 mmol) and diethyl(diazo-methyl)phosphonate (BOR 2 275 mg, 1.25 mmol) in dry EtOH (10 mL) was added CS2CO3 (480 mg, 1.5 mmol) at 0 °C and the resulting mixture was stirred at room temperature until complete consumption of aldehyde 1 (monitored by TLC). To the reaction mixture containing alkyne intermediate were then added Cul (19 mg, 0.10 mmol), BOR (2 165 mg, 0.75 mmol) and KOH (56 mg, 1 mmol) and stirring continued until all the alkyne intermediate was coti-sumed (monitored by TLC). Then the reaction mixture was concentrated in vacuo and the crude residue was directly subjected to silica gel column chromatography ( -hexane/ethyl acetate 3/ 7) to afford pure phosphonylpyrazole 4, characterized by spectral studies. 

A 9-(HuoroaIkenyl)adenine derivatives containing a pendant aikynyl-phosphonate group have been synthesised by similar methods. Upon subjecting adenine to an initial alkylation with diethyl (3,4-dibromo-l,l-dilluorobut-2-en-l-yl)phosphonate, a series of eliminations took place in the presence of TBAF to afford an intermediate l, 3 -diyne-phosphonate 137 [152] (Scheme 50). Further reaction with TBAF was found to fadhtate fluoride attack alpha to N-9 to afford the corresponding A/9-(fluoroaIkenyl)purine 138. 

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