Metal ion electrophilic catalysis has been revealed in ring opening reactions of 1,2-epoxides 1-5 promoted by complexes of polyethers 6-9 with alkali metal halides MHal (M+ = Li+, Na+, K+; Hal(-) = I-, Br-) in solvents of low polarity (chlorobenzene, 1,2-dichlorobenzene). The catalytic effect depends on the Lewis acid character of the cation (K+ <<Na+ < Li+) as well as on the ligand topology (open-chain > cyclic polyether). Results have been rationalized on the basis of a transition state where the complexed cation (M+ subset of Lig) stabilizes the negative charge developing on the oxygen atom of the oxirane ring while favors the nucleophilic attack at the adjacent carbon by the halide anion Hal(-).
Ring opening reactions of 1,2-epoxides catalyzed by complexes of polyether ligands with metal halides in low polarity solvents. Comparison with heterogeneous systems / D. Landini, A. Maia, C. Pinna. - In: ARKIVOC. - ISSN 1551-7004. - 2004:3(2004), pp. 202-212.
Ring opening reactions of 1,2-epoxides catalyzed by complexes of polyether ligands with metal halides in low polarity solvents. Comparison with heterogeneous systems
D. Landini;C. Pinna
2004
Abstract
Metal ion electrophilic catalysis has been revealed in ring opening reactions of 1,2-epoxides 1-5 promoted by complexes of polyethers 6-9 with alkali metal halides MHal (M+ = Li+, Na+, K+; Hal(-) = I-, Br-) in solvents of low polarity (chlorobenzene, 1,2-dichlorobenzene). The catalytic effect depends on the Lewis acid character of the cation (K+ <Pubblicazioni consigliate
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