从石油化工产品中任选一种三个碳的烃为唯一碳源和有关物质为原料合成

二甲酸乙二酯，（           ）写出各步反应的化学方程式。（可不注明反应条件）
已知：

（R₁、R₂、R₃、R₄、可代表烃基，也可代表氢原子）
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