Cyclic esters of phosphoric acid

D. Cyclic Esters of Phosphorous Acid.—There has been some controversy about the stable stereochemistry at phosphorus in cyclic phosphites and phosphonites this now appears to be resolved by agreement in a series of papers. The stereochemistry of 2-alkoxy-4-methyl-l,3,2-dioxaphosphorins... 

Cyclic Esters of Phosphorous Acid.—A large number of 2-substituted-4-methyl-l,3,2-dioxaphospholans (88) have been prepared and their stereochemistry and conformations investigated by 1H and 31P n.m.r.69 Unlike the corresponding 1,3-dioxans, the tra/w-isomer (88a) is favoured in all cases, and each isomer is best described in terms of two rapidly equilibrating half-chair conformers with the 4-alkyl group pseudo-axial or pseudo-equatorial. 

The hydrolysis in acid or base of five-membered cyclic esters of phosphoric acid proceed some 10 times faster than their acyclic analogs or the six- and seven-membered cyclic phosphates 55 56. Unlike that of dimethyl phosphate, the hydrolysis of hydrogen ethylene phosphate is accompanied by rapid oxygen exchange into the unreacted substrate57, viz-... 

S. Penczek, Polymerization of cyclic Esters of Phosphoric Acid, Pure Appl. Chem. 48, 363 (1976). 

An increasing number of investigators are interested in the propagation of cyclic monomers without carbon. The reasons are theoretical interest and anticipation of the future need of monomer sources other than the fossil fuels. Theoretically siloxane units can be arranged into lamellae or bundles (an analogy of mica or asbestos) yielding thermoplastic materials. Another possibility could be the application of the cyclic esters of phosphoric acid [326], phosphazenes, etc. 

Polymerization of cyclic esters of phosphoric acid (cyclic phosphates) is interesting from the synthetic point of view, because the resulting polymers have the sequence of atoms of the chain identical with this, which appears in important biopolymers such as nucleic or teichoic acids. Both 5- and 6-membered cyclic phosphates undergo polymerization. 

Some cyclic amines, iminoethers, sulfides, ethers, esten, and acetals were indeed demonstrated to polymerize without appreciable transfer and/or termination. It cannot be excluded that for monomers belonging to other compound classes, e.g. lactams or cyclic esters of phosphoric acid, the conditions for the transfer- and terminationless processes will be found in the near future. 

A simple alkylation, without any side reactions was also observed in the initiation of cyclic sulfides and of cyclic esters of phosphoric acid 2-methoxy-2-oxo-l,3,2-dioxaphosphorinane) ° In the latter case, the tetraalkoxyphosphonium ion is formed (the phosphoryl oxygen atom is alkylated) as follows ... 

This treatment was applied to the polymerization of 3,3-bis-(chloromethyl)-oxetane (irreversible propagation) and, more recently, to the polymerization of cyclic esters of phosphoric acid (reversible propagation) ... 

Cyclic Esters of Phosphorous Acid.— Two groups have investigated the conformational preference of amino-substituents on phosphorus in 1,3,2-dioxaphosphorinans. Dipole moment and n.m.r. measurements show that... 

Adenosine 3 -5 -cyclic monophosphate (cyclicAMP or cAMP) is an important regulator of a large number of biological processes. It is a cyclic ester of phosphoric acid and adenosine involving the hydroxyl groups at C-3 and C-5. ... 

The synthesis of polyphosphates as a model for nucleic and teichoic acids by ring-opening polymerization of cyclic esters of phosphoric acid is studied by Penczek s group and was reviewed recently (43. 101. 102). 

Another way of determining whether the observed plateau does really correspond to [M]e is to perform polymerization at various ratios of [M to [I]0. The properly determined value of [M]e should be independent of this ratio, provided that [M]o/[I]o is not too small. Thus, for non-living systems it is necessary to carry out polymerizations with increasing initial initiator concentration until a constant ultimate monomer conversion is reached. This method of approaching the equilibrium concentration gave reliable thermodynamic parameters for the cationic polymerization of cyclic esters of phosphoric acid, in spite of termination observed in these systems 11 ... 

The size of substituents may also influence the polymerizability of cyclic monomers. This was shown for the cationic (and anionic) polymerization of cyclic esters of phosphoric acid 11... 

Cyclic Esters of Phosphorous Acid.—The conformational analysis of a number of 2-substituted-2-phospha-l,3-dithiacyclohexanes (121) and (122) has been carried out. The free energy for cis-trans equilibrium in (121) was determined, and although n.m.r. showed that the tertiary butyl group... 

The organization of this Chapter has been changed somewhat from last year. Phosphonous and phosphinous acids and their derivatives, and cyclic esters of phosphorous acid, are not discussed separately from phosphorous acid and its derivatives, because of the similarity of the reactions involved. Two-co-ordinate phosphorus compounds are treated in a separate section like last year phospha-alkenes without phosphorus-heteroatom bonds are not covered. 

In the polymerization of the srx-membered cyclic esters of phosphoric acid (dioxaphosphorinanes)... 

Thus cationic polymerizability could only be related to the entropy of activation as desaibed in this chapter for cyclic esters of phosphoric acid. Most probably substituents and the related polymer linear units are getting enhanced statistical probability of states in the transition state. One could expect dependence on basicity, but the known basicities are almost the same and do not change monotonically (given in ADy (m )) OX 103 MOX 106 DMOX 99. Thus, like in polymerization of cyclic esters of phosphoric acid, where the thermodynamic reactivity is governed by entropy change, this is the kinetic reactivity depending on the change of entropy of activation. 

Among the tetracoordinated cyclic esters of phosphoric acid, 2-alkoxy-2-oxo-l,3,2-dioxaphosphorinanes (19) have been studied in detail. Trityl salts (PhsC A", where A=Pp6, Asp6, SbPe) and/or triflic esters (CFsSOsMe and... 

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