Reactions of Aryl 5‐substituted‐2‐Thiophenecarboxylates Promoted by 4‐Z‐C6H4O −/4‐Z‐C6H4OH in 20 mol % DMSO(aq). Effect of Nucleophile on Acyl‐Transfer Reaction

摘要

Nucleophilic substitution reactions of 5a??XC4H2 (S)C(O)OC6H3 a??2a??Ya??4a??NO2 (1) promoted by 4a??Za??C6H4O a??/4a??Za??C6H4OH in 20a??mol % dimethyl sulfoxide (DMSO)(aq) have been studied kinetically. The reactions exhibited seconda??order kinetics with ?2acyla??=a??a??2.52 to a??2.83, ??(x)a??=a??2.81a??3.16, ?2nuca??=a??0.88a??0.04 and ?2lga??=a??a??0.94, respectively. The results have been interpreted with an additiona??elimination mechanism in which the nucleophilic attack occurs in the ratea??determining step. Comparison with existing data reveals that the ratea??determining step changes from the second to the first step by the change in the nucleophile from R2NH/R2NH2 + to 4a??Za??C6H4O a??/4a??Za??C6H4OH.