Structural features of cleavage of nonsymmetrically substituted 1,3-dioxolanes by the Grignard reagent

1. The reaction between 4-methyl- and 2,4-dialkyl-1,3-dioxolanes and the Grignard reagent shows specific structural features, since only one of the possible hydroxyl ethers is formed. 2. IR spectroscopy and GLCH analysis were used to determine the structures of the hydroxy ethers; based on these findings, it was shown that the Grignard reagent splits the nonsymmetrically substituted dioxolanes under study at the O1-C2 bond. 3. The reaction is selective with respect to the spatial isomers of 2,4-dialkyl-1,3-dioxolanes (the cis-isomer reacts faster). 4. The reaction of 4-methyl-1,3-dioxolane with ethylmagnesium bromide was used as an example to show that insoluble solvates form at the first reaction stage; these consist mainly of a complex of cyclic acetal with magnesium bromide. 5. The findings agree with a mechanism involving cyclic migration of electrons in the six-membered ring formed by the complex “acetal-magnesium bromide” and magnesium diethyl.