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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