We recently showed that niobium and tantalum pentahalides, MX5, suspended in chlorinated solvents, react readily with simple oxygenated organic molecules (ketones, aldehydes, amides, ureas, cyclic ethers) affording Lewis acid-base adducts. Subsequent C–H or C–O bond activation has been observed in a number of cases.1,2 Interestingly, when an excess of 1,2-dimethoxyethane (dme) is added to MX5 (M = Nb, Ta, X = Cl, Br, I), final formation of MOX3(dme), CH3X and 1,4-dioxane takes place, as result of unusual dme activation, see Figure 1.3 Analogously, the reaction of 1,2-dimethoxypropane with NbCl5 yields 2,5-dimethyl-1,4-dioxane, indicating a new route for the expeditious synthesis of methyl-substituted dioxanes (Figure 1). The role played by the halide and the influence of the stoichiometry employed will be discussed.

From 1,2-dialkoxyalkanes to 1,4-dioxanes: a room temperature transformation mediated by group 5 metal halides

MARCHETTI, FABIO;PAMPALONI, GUIDO;
2008

Abstract

We recently showed that niobium and tantalum pentahalides, MX5, suspended in chlorinated solvents, react readily with simple oxygenated organic molecules (ketones, aldehydes, amides, ureas, cyclic ethers) affording Lewis acid-base adducts. Subsequent C–H or C–O bond activation has been observed in a number of cases.1,2 Interestingly, when an excess of 1,2-dimethoxyethane (dme) is added to MX5 (M = Nb, Ta, X = Cl, Br, I), final formation of MOX3(dme), CH3X and 1,4-dioxane takes place, as result of unusual dme activation, see Figure 1.3 Analogously, the reaction of 1,2-dimethoxypropane with NbCl5 yields 2,5-dimethyl-1,4-dioxane, indicating a new route for the expeditious synthesis of methyl-substituted dioxanes (Figure 1). The role played by the halide and the influence of the stoichiometry employed will be discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/202804
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