Alkylene phosphite, cyclic

T0 prepare models of TA, the corresponding cyclic alkylene phosphoric acids cannot be directly polymerized because the presence of acidic protons of the phosphate group makes the ionic polymerization impossible. Thus, cyclic phosphorus compounds with blocked third functions have to be used. These are phosphates., phosphoramidates and phosphites. After polymerization the obtained polymer is converted by deblocking into the polyalkylene phosphate, e.g. polysalt or polyacid form. 

Several methods have been reported for the preparations of these polymers. The most versatile involves poly(alkylene phosphonate)s as intermediates. The polymers can be prepared by a variety of methods. Two of the most promising appear to be the ring opening polymerizations of cyclic phosphonate monomers [2-8,13] and the condensation polymerizations of dimethyl phosphite and dialcohols [9,11]. These methods yield polymers with number-average molecular weights (Hj,) ranging from 10 to 10 daltons. 

The scheme for the preparation of the poly(alkylene phosphonate)s and poly(alkylene phosphate)s via ring-opening polymerizations is given in Figure 2. This can be separated into two phases 1) the ring-opening polymerizations of the cyclic phosphites to form the poly(alkylene phosphonate)s and 2) the conversion of the poly(alkylene phosphonate)s to poly(alkylene phosphate)s. These procedures are modifications of those reported in the literature and are discussed below. 

L-Ascorbic acid has been converted to the cyclic alkylenephosphites 49 by reaction with alkylene chlorophosphites, and to the 2, 3 -cyclic phosphites 50 by treatment with phosphinidyne triimidazole followed by isopropylideneglycerol. Compounds 49 and 50 were treated with sulfur or selenium to give the corresponding thio- or seleno-phosphates. The 2-phosphate 51 of 5,6-0-isopropylidene-D-eo t ro-ascorbic acid was prepared by use of POCI3 under basic conditions. As minor by-products, the 2-diphosphate and the 2,2 -phosphodiester were formed. ... 

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