Potassium Cryptate Catalysis in the Elimination Reaction of a Sulfonate Ester

Article abstract of DOI:10.1021/ja00054a002

In the reaction of p-nitrophenyl methanesulfonate (1) with alkali-metal ethoxides, it is found that potassium ethoxide in the presence of excess 2.2.2 cryptand is more reactive than potassium ethoxide alone or in the presence of excess 18-crown-6.An upward curvature in the plot of k_obs vs _o in the presence of 2.2.2 cryptand is interpreted as arising from parallel reactions of free ethoxide ion and the ion pair of ethoxide ion with cryptated potassium ion ( 2.2.2>⁺EtO^-), the latter being more reactive than the former.It is shown that the ester reacts predominantly by an E1cb-type elimination mechanism, and the potassium cryptate appears to stabilize the transition state for leaving-group departure by electrostatic interactions through an 18-membered ring "window" in the cryptand.