Oxazolidone mechanism

The product anion (V) decarboxylates (18b) on acquiring a proton from an acid species present (e.g. the conjugate acid BH of the initiating base product in (6) or an NCA molecule). Formation of species such as (VI) diversifies the routes to polymerization. Thus (VI) is a primary base and can react by the mechanism already described with any oxazolidone-2,5-dione system present, including monomer (I) or a molecule of its own kind. These processes are indicated in (19a) and (19b), respectively. 

Nitro-4,4-bis(acetoxymethyl) oxazolidone stirred mechanically with ca. N NaOH below 35° for 2 hrs., then treated with an amount of HOI exactly equivalent to the NaOH used — tris (hydroxymethyl) methyl-nitramine. Y 77%. (J. Cason and F. S. Prout, Am. Soc. 71, 1218 (1949).)... 

Although several attempts have been made to explain the formation of the oxazoles and oxazolidones from a common intermediate (previously reviewed),1-4 the mechanism of the reaction is not yet completely understood. Further, the synthesis is not unambiguous as it may give a mixture... 

The nature of the photopolymerizable components such as chemical stmcture, molecular weight, and functionality plays a significant role in the efficiency of the polymerization reaction and physical, chemical, photochemical, mechanical, and stmctural properties of the cured system. When monomers or multifunctional monomers are combined with oligomers, such as in the case of carbonate, carbamate, or oxazolidone acrylates, they become highly reactive, exhibit low residual saturation and good flexibility. " " The mechanical properties sharply increase with functionality of the monomer with an increase in the cross-linking density, but they become more brittle. Solubility, biocompatibility, thermal resistance. 

The polymers were prepared by reacting five glycidyl ethers with 4, 4 -diisocyanatodiphenylmethane in the presence of 2-ethyl-4-methylimidazole. The degree of cure of the resins was followed by IR spectroscopy and DSC. The rates of the isocyanurate to oxazolidone linkages were determined quantitatively by an infrared method and the glass transition temperatures of the polymers were measured by DSC and dynamic mechanical thermal analysis. 16 refs. 

If this mechanism (Reaction 2) is correct the oxazolidone formation... 

An alternative mechanistic explanation for the formation of oxazolidone, derived from the reaction of isocyanate and epoxide, has been given by Gulbins et al. (Reaction 4), Here the oxide anion derived from the epoxy ring attacks the carbonyl (C 0), rather than the imino (C N) double bond as shown in Reaction 2, Ring closure then produces an N-substituted imino-1,3-dioxolane, which isomerises to the 2-oxazolidone. Support for this mechanism was gained from the isomerism of an N-phenyl-2-imino-l,3-dioxolane to the corresponding 2-oxazolidone, using the same reaction conditions. 

Decomposition of the 7V-nitroso-oxazolidone (163) with base in a solution of ethoxyacetylene gives the allene diethylacetal (164) the carbene intermediate in the suggested mechanism is supported by previous work. ... 

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