Aminocyclodextrins to facilitate the deprotonation of 4-tert-butyl-α- nitrotoluene

6^A-Amino-6^A-deoxy-β-cyclodextrin enhances the rate of the deprotonation of 4-terf-butyl-α-nitrotoluene. The rate constants for reaction of the cyclodextrin-bound species, k_inc = 4 × 10^-3, 9 × 10^-3 and 19 × 10 ^-3 s^-1, at pH 6.0, 6.5 and 7.0, respectively, in 0.1 mol dm^-3 aqueous phosphate buffer containing 1% methanol at 298 K. These rate constants correspond to a rate acceleration (k_inc/k _un) of ca. 10 times at each pH. Under the same conditions, 6 ^A-dimethylamino-6^A-deoxy-β-cyclodextrin and 6 ^A-(2-aminoethylamino)-6^A-deoxy-β-cyclodextrin are more effective; at pH 6.0, 6.5 and 7.0, for the former, k_inc = 3 × 10^-2, 7 × 10^-2 and 12 × 10 ^-2 s^-1, whilst for the latter, k_inc = 4 × 10^-2, 5 × 10^-2 and 9 × 10^-2 s ^-1, respectively. Each cyclodextrin also decreases the pK_a of the nitrotoluene, from 6.8 in free solution, to 6.2 when bound. The accelerated deprotonation by 6^A-amino-6^A-deoxy-β- cyclodextrin is reflected in the enhanced rates of hydrogen-deuterium exchange of the nitrotoluene in deuterium oxide, and in the conjugate addition of the nitrotoluene to methyl vinyl ketone in aqueous solution.