NEW CHIRAL CROWN-ETHERS DERIVED FROM CAMPHOR AND THEIR APPLICATION TO ASYMMETRIC MICHAEL ADDITION - FIRST ATTEMPTS TO RATIONALIZE ENANTIOSELECTION BY AM1 AND AMBER CALCULATIONS

The synthesis of novel optically active crown ethers derived from (1R)-(+)-camphor is described. The mechanism of their catalytic effect upon the Michael addition of phenylacetate to acrylate is discussed in terms of kinetic vs. thermodynamic control in the formation of the catalytic ion-pair complexes. The relative basicity of the complexes formed between the alkaline metals and the unprotonated chiral crown ethers plays an important role in the sterochemical outcome. AMBER and AM1 calculations support that the reaction in which the best e.e. (83%) is obtained proceeds under kinetic control.