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;
2008-01-01
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
