ECHET96 Search CD [Molecules: 8] [Related articles/posters: 043 023 008 114 050 ]

Catalysis by alkaline earth cations in nucleophilic aliphatic substitution of crown ethers derivatives

Catalysis by alkaline earth cations in nucleophilic aliphatic substitution of crown ethers derivatives

Cristina Casadio, Giancarlo Doddi* and Paolo Mencarelli*

Dipartimento di Chimica and Centro CNR di Studio sui Meccanismi di Reazione, Universita' "La Sapienza", P.le Aldo Moro 2, 00185 Roma, Italy

Our interest in the effects of host-guest interactions of alkali or alkaline-earth cations on the thermodynamic and kinetic reactivity 1 prompted us to study the role of these species on nucleophilic aliphatic substitution reactions of crown ethers derivatives. In particular, we are interested in evaluating the role of a polyoxyethylene side arm linked to a crown ether moiety on the stabilization of ground and transition states of these reactions.

Here we present results obtained for the catalysis of alkaline earth cations Sr2+ and Ba2+ on the nucleophilic aliphatic substitution of the lariat ether 7-2',5',8',11',14'-pentaoxacyclopentadecyl-3,6-dioxaheptyl tosylate 1 with MeO- ion, in MeOH, at 40 C, to yield the corresponding methoxy derivative 9-2',5',8',11',14'-pentaoxacyclopentadecyl-2,5,8-trioxanonane 2.

7-2',5',8',11',14'-pentaoxacyclopentadecyl-3,6-dioxaheptyl tosylate 1

9-2',5',8',11',14'-pentaoxacyclopentadecyl-2,5,8-trioxanonane 2

Previous results

Present results

References