Unexpected cleavage of ether bonds of 1,3-dimethoxypropane in Grignard–Wurtz synthesis of a MgCl2–donor adduct

•1,3-Dimethoxypropane was cleaved in Grignard–Wurtz synthesis of MgCl2–donor adduct.•A Grignard reagent, BuMgCl most likely causes the cleavage reaction.•Final product of the reaction is methoxymagnesium chloride.•There seem to be at least two reaction paths occurring in parallel.•1-Heptene and propene are formed as by-products in the cleavage reaction.

Diethers are an important group of electron donors in Ziegler–Natta catalysts. A simple diether, 1,3-dimethoxypropane was studied as an electron donor in Grignard–Wurtz synthesis of a MgCl2–donor adduct. 1,3-Dimethoxypropane was unexpectedly found to undergo a cleavage reaction during the synthesis producing methoxy groups (OCH3). Each mole of 1,3-dimethoxypropane produced approximately 2 moles of methoxy groups, which are probably bound to magnesium chloride as methoxymagnesium chloride. A Grignard reagent, BuMgCl formed in the Grignard–Wurtz reaction most likely causes the cleavage of the ether bonds in 1,3-dimethoxypropane and there seem to be at least two parallel reaction paths taking place and producing at least two different by-products. The first step in the cleavage of 1,3-dimethoxypropane is a Grignard reagent (BuMgCl) induced elimination of OCH3, which gives 3-methoxy-1-propene. This intermediate product reacts further in a substitution reaction caused by the Grignard reagent producing 1-heptene as the by-product. The cleavage of the ether bond in 3-methoxy-1-propene and formation of OCH3 can also occur through another reaction path, which produces propene as the by-product.

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