The Hydrolysis of Five-Membered Cyclic Phosphotriesters to Cyclic Phosphodiesters

Synthesis of Novel 1,2-Diphenylpyrrole Derivatives Using Organophosphorus Reagents and Their Antitumour Activities

“…The formation of 11a-c involves nucleophilic attack 22,23 by the phosphite on the active carbonyl carbon in 1 to give the zwitterionic intermediate D. Addition of a molecule water (unavoidable moisture) to intermediate D produces a transient intermediate E with pentacovalent phosphorus. 24,25 The latter collapses through loss of dialkylphosphite, followed by loss of one molecule of water to give the final products 11ac. The dialkylphosphites were detected in the water layer by the development of a violet colour on addition of 3,5-dinitrobenzoic acid.…”

“…Similarly, when 1 was allowed to react with excess of triethylphosphite 5b or triisopropylphosphite 5c, adducts 11b or 11c were isolated (Scheme 3). The formation of 11a-c involves nucleophilic attack 22 24,25 The latter collapses through loss of dialkylphosphite, followed by loss of one molecule of water to give the final products 11ac. The dialkylphosphites were detected in the water layer by the development of a violet colour on addition of 3,5-dinitrobenzoic acid.…”

Mechanisms of Nucleophilic Substitution in Phosphate Esters

“…Confirmation that the presence of the five-membered phospho diester ring in a molecule labilizes nucleophilic attack at phosphorus, even when the ring remains intact in the reaction product, has recently come from other sources (38,68,196).…”

“…by the failure of the phosphoryl group to exchange oxygen with the solvent prior to hydrolysis. Although pentaalkoxyphosphoranes, (RO)6P, have been characterized (194,196,197), the reaction cannot, then, proceed by an addition-elimination sequence analogous to that believed to represent the course of hydrolysis of carboxylic acid esters (24a), but must consist either of a one-step process in which the leaving group is being expelled at the same time the substituting group is entering (Eq. 2) or of a two-step process in k, E, log PZ, Temp., °C.…”

Phosphorylation by means of cyclic enediol phosphates

“…Compounds with the CEP group are extremely reactive, being examples of highly strained five-membered cyclic phosphates.27, 28 In mechanistic terms (Scheme (23) For a compilation of basic papers on the oxyphosphorane intermediate hypothesis in nucleophilic displacements at P(4), see ref 24. The direct observation of a hydroxyphosphorane in equilibrium with a phosphate ester has been reported (ref 25).…”