2- Methoxy-2-oxo-l,3,2-dioxaphospholane

Preparation 6-1 2-Methoxy-2-oxo-l,3,2-dioxaphospholane is synthesized by a modified Edmundson method (31,35-37). Phosphorus tinchloride is allowed to react with ethylene glycol dry 1,2-dichloroethane. The 2-chloro-l,3,2-dioxaphospholane is oxidized to give 2-chloro-2-oxo-l,3,2-dioxaphospholane. Finally this intermediate is reacted with methanol to give the desired 2-methoxy-2-oxo-l,3,2-dioxaphospholane. The synthesis is shown in Figure 6.11. 

Poly(phosphoester)s are polyphosphates obtained through ring-opening polymerization of cyclic phosphoester monomers poly(2-methoxy-2-oxo-l,3,2-dioxaphospholane), or poly(methyl ethylene phosphate), is not reported to show the LCST tjehaviour poly(phosphoester)s are biodegradabile and biocompatible [433-438]... 

Methoxy-2-oxo-l,3,2-dioxaphospholanes (10) ethoxy-2-oxo-l,3,2-dioxaphospholanes (11) were polymerized over a wide range of temperatures, namely, from -20 to 120 C... 

The mechanism of anionic polymerization of 2-methoxy-2-oxo-l,3,2-dioxaphospholane (10), initiated by (PPOjsAl, was discussed in detail previously. Polymerization proceeds through the formation of the polymeric AI-OCH2CH2-... bond. The proposed mechanism of polymerization can be visualized through the successive reactions (cf eqn [25]). ... 

Bis-rethoxy-ethyl-phosphano]- XII/1, 215 Bis-[ethyl-propyloxy-phosphanoJ- XII/1, 215 Bis-[4-methoxy-2-oxo-l,3,2-dioxaphospholan-2-yloxy] XII/2, 909... 

Much work has been done on configuration and conformation, e.g. of 2-methoxy-2-oxo-4,5-diphenyl-l,3,2-dioxaphospholanes with 170 and lsO labelled reagents (81CC245). A large number of 2-dimethylamino-l,3,2-dioxaphospholanes or 3-methoxy-2-methyl-l,3,2,-oxazaphospholanes are mentioned in a recent publication, in which spiro compounds of the general structure (108) were prepared by addition to diethyl azodicarboxylate (equation (69)) (80PS(8)147>. 

Enthalpies of activation of both reactions, proceeding with rate constants kiand k2 are nearly the same for 2-methoxy substituted monomer. Ratio ki/k2 = 3 was calculated in 40° and 100°. 2-Neopenthoxy substituted monomer does not participate in Arbuzov type transfer and the rate constant ki is approximately 40 times lower than for 2-methoxy derivative. When substituent was changed to t-buthoxy group decomposition of intermediate salt into isobutylene, 2-hydro-2-oxo-l,3,2-dioxaphospholane and 2-methyl-2-oxo-l,3,2-dioxaphospholane was observed. 

In contrast, 4,5-dimethyl-2-methoxy-l,3,2-dioxaphospholane reacts sluggishly with ethyl chloroacetate and only ethyl bromoacetate leads to the desired five-membered cyclic phosphonates as mixtures of the racemic and meso isomers. The 2-ethoxy-benzo[l,3,2]dioxaphosphole on reaction with chloro-, bromo-, or iodoacetate at 200-230°C leads to the 2-(ethoxycarbonyl)methyl-2-oxo-benzo[l,3,2]dioxaphosphole in variable yields (42-58%). ... 

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