From Carboxytelomerization of 1,3-Butadiene to Linear α,ω-C -Diester Combinatoric Approaches for an Efficient Synthetic Route.

Two novel reaction pathways were tested to synthesize the linear α,ω-C -diester exclusively from three basic reagents: 1,3-butadiene, carbon monoxide and methanol. Therefore, carboxytelomerization of 1,3-butadiene and methanol was merged with methoxycarbonylation in two different ways to obtain highly linear C -diester. Through a palladium-based and -assisted tandem catalytic system, 22 % yield of the desired C -diester was obtained without isolating the intermediates. Subsequently, the limitations of the novel assisted tandem catalytic concept were uncovered and based on that, a two-step reaction regime was established. By optimization of the carboxytelomerization, the C -monoester as intermediate could be formed in nearly quantitative yields and excellent linearity. In a second reaction step, the isolated monoester was successfully converted by methoxycarbonylation into the desired linear C -diester in overall yields up to 84 %.