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2-Methylene-1,3-dioxepane is used in the synthesis of functional 2-methylene-1,3-dioxepane terpolymer which functions as a building block for the construction of biodegradable pH sensitive polymeric prodrug for intracellular drug delivery.

2-Methylene-1,3-dioxepane (MDO), which is also called cyclic ketene acetals (CKAs), can undergo radical addition on their carbon–carbon double bond, which then subsequently leads to propagation, either by ring opening or ring retaining or by a combination of both, which depends especially on their structure. This monomer provides a novel and alternative synthetic route for the synthesis of polycaprolactone, and it imparts degradability to conventional vinyl monomers by introducing ester linkages into the backbone. Thereby, the structure of the polyester material can be greatly expanded, and the polyester material can be applied to a wider range of fields. Its same repeat unit with poly(ε-caprolactone) (PCL). On the same time, the PCL synthesis through rROP offered new characteristic properties, such as totally amorphous instead of semicrystalline, versatile functionalization abilities by copolymerization with different vinyl monomers[1-2].

General procedure for the synthesis of 2-methylene-1,3-dioxane from 2-chloromethyl-1,3-dioxane (cas:54237-96-6) and sec-butanol: In a four-necked, 1-liter round-bottomed flask fitted with a thermometer, a reflux condenser, a pressurized dosing funnel, and a mechanical stirrer, 62.5 g of potassium hydroxide and 47 g of sec-butanol were added. The mixture was heated to 125 °C until all potassium hydroxide particles were completely dissolved. Subsequently, 37.5 g of 2-chloromethyl-1,3-dioxane synthesized according to the method of Example 1 was slowly added dropwise through the addition funnel. After the dropwise addition was completed, the reaction was continued for 2 hours. After completion of the reaction, the heating was stopped and 100 g of distilled water and 50 g of toluene were added to the reaction mixture. The mixture was transferred to a separatory funnel and the organic phase was separated. A sample of the reaction mixture was analyzed by gas chromatography to confirm that 2-chloromethylidene-1,3-dioxepane was completely converted and that the crude yield of 2-methylidene-1,3-dioxepane was 72%.

[1] Xu P, et al. Hyperbranched Polycaprolactone through RAFT Polymerization of 2-Methylene-1,3-dioxepane. Polymers, 2019; 11: 318.
[2] Ding D, et al. Degradable Copolymer of 2-Methylene-1,3-dioxepane and Vinyl Acetate by Photo-induced Cobalt-Mediated Radical Polymerization. Polymer Chemistry, 2016; 7: 5258-5264.