Reactions of primary amines and alcohols with 4-toluoyl azide.
Primary amines RNH2 [2: R = n-butyl(2a), cyclohexyl (2b), 3-pentyl (2c)] react with 4-toluoyl azide in non-nucleophilic solvents in a clear second order reaction, which is strongly dependent on the size of the amine and the solvent polarity [k(acetonitrile; 25 Deg):15.51(2a), 0.83(2b) and 0.19(2c)L/mol.min; DH# = 22.1 kJ/mol, DS# = -170.5 J/mol.K[2b in acetonitrile]]. Drastic changes occur in the presence of nucleophilic solvents. With nucleophilic amines 2 added to these in the soln. a concurrent reaction with alcs. R1OH [4: R1= Me (4a), Et (4b), Bu (4c)] yielding 4-toluoyl esters (5 :4-MeC6H4CO2R1, R1 as above) is obsd. This is esp. dominating with the smallest alc. methanol (4a) and/or effectively promoted by bulky amines (2b, 2c; up to 99% 5a). Compared with the pure alcoholysis a huge acceleration of the ester formation, proportional to the concn. of the nucleophilic amine 2, is obsd. The reaction mechanism is discussed with special emphasis on steric effects in the competition of nucleophiles for toluoyl azide .
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