Dichloro phosphonates, synthesis

We found that dichloro diorgano silanes are suitable reagents for the synthesis of diorgano bis(0-alkyl)phosphonates. A different reactivity of both chlorine atoms of the silanes is observed in the dealkylation reaction of dialkylphosphonates in contrast to Me3SiBr [2]. 

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

Durette et al. [74] have achieved the total synthesis of the hexadepsipeptide antibiotic L-156,602 128) using the mixed phosphonic anhydride method as key macrolactamization step. As shown in Scheme 43, treatment of the linear depsipeptide 126 with n-propylphosphonic anhydride and DMAP in dichloro-methane at high dilution afforded the macrocycle 127 in more than 57% yield. 

Similarly, the a-monochlorinated and a-monobrominated dimethyl 2-oxoalkylphosphonates are prepared in satisfactory yields (50%) by reaction of the sodium enolate of dimethyl 2-oxoalkyl-phosphonates with NCS or NBS in DME at room temperature- "- - or with bromine in Et20 (53-71%) or THE (60%) Synthesis of diethyl l-chloro-2-oxopropylphosphonate has also been reported through reduction of the 1,1-dichloro derivatives with sodium sulfite.- lodination in the Y-position of P-ketophosphonate 1,3-dianions prepared with KiCO, in MeOH has been reported. These dianions react with benzaldehyde in a Homer-Wadsworth-Emmons-Darzens reaction sequence to produce the a,P-unsaturated a, P -epoxyketones in 60-79% yields (Scheme 7.101).s ... 

Finally, Schmidt and coworkers have similarly applied the hydroxylation of phosphonates for synthesis of some sialyltransferase inhibitors. Thus, the stabilized enolate of 71 was selectively oxidized using dichloro(camphorsulphonyl)oxaziridine (6) to produce the a-hydroxy diallylphosphonate in low yield but as a single stereoisomer. The reaction was also found to be effective for compounds containing a variety of ring substituents.59,60... 

He HW, Xu L, Liu ZJ (1999) A convenient synthesis of l-(dichloro-pyrimidinyl carbamyloxy) alkyl phosphonates. Phosphoms, Sulfur Silicon Relat Elem 147 937-938... 

Wang T, He HW (2004) An efficient synthesis of a-(2,4-dichloro-phenoxyacetoxy)aryl methyl phosphonate monosodium salts. Synth Commun 34 1415-1423... 

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