- STRUCTURE AND REACTIVITY OF CYCLIC ENEDIOL N-PHOSPHORYLAZOLES AND N-PHOSPHORYLTETRAMETHYLGUANIDINE
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A series of cyclic enediol phosphorylazoles (CEP-azoles) derived from the 4,5-dimethyl-2-oxo-1,3,2-dioxaphosphole ring system and pyrrole, imidazole, 1,2,4-triazole and tetrazole have been prepared.The structures of CEP-triazole and of the related phosphoramidate CEP-tetramethylguanidine (CEP-TMG) have been determined by X-ray crystallographic analysis and compared with the known structure of CEP-imidazole.The reactions of CEP-azoles and CEP-TMG with alcohols have been studied and compared with the reactions of CEP-esters, CEP-OR1, with alcohols, R2OH, under catalysis by the azoles or tetramethylguanidine.Relative rates of reactions and differences in product composition are discussed in terms of the formation of an oxyphosphorane intermediate in nucleophilic substitutions at 4-coordinate phosphorus.Differences in reactivities among the CEP-derivatives have been determined from the occurence and direction of the following reactions: CEP-Azole1 + Azole2 -> CEP-Azole2 + Azole1; CEP-Azole + TMG -> CEP-TMG + Azole
- Ramirez, Fausto,Ricci, John S.,Okazaki, Hiroshi,Marecek, James F.,Lewy, Mark
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p. 279 - 300
(2007/10/02)
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- Reactions of Phosphodiester Anions with Phosgene
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The mechanisms of reactions of phosgene with the N-methylpyridinium salts of diphenyl phosphate and 1,2-dimethylethenylene phosphate (or 4,5-dimethyl-2-oxido-2-oxo-1,3,2-dioxaphosphole) have been studied by 31P NMR spectrometry in dichloromethane at various temperatures and molar ratios of reactants.The products are mixtures of pyrophosphates and phosphorochloridates in proportions that vary with the structure of the phosphodiester and the experimental conditions.The reactions have also been carried out in benzene suspension.The conditions can be adjusted to give exclusively and in high yields (over 85percent) either bis(1,2-dimethylethenylene)pyrophosphate or 1,2-dimethylethenylene phosphorochloridate (or 2-chloro-4,5-dimethyl-2-oxo-1,3,2-dioxaphosphole).These cyclic enediol phosphoryl derivatives are excellent reagents for the synthesis of complex biological phosphodiesters.
- Ramirez, Fausto,Marecek, James F.
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p. 847 - 850
(2007/10/02)
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