Heteroaromatic azo-activated substitutions. Part 3. Catalysis in the reaction of 4-(4-methoxyphenylazo)pyridinium methiodide with amines in dipolar aprotic solvents. Kinetic form and the mechanism of the uncatalysed reaction in nucleophilic aromatic substitution

Abstract

088ChemInform Abstract The kinetics of the reactions of the title compound (I) with the following sec.-prim. amine (II) pairs are studied: in DMSO: piperidine-butylamine and morpholine-benzylamine, in MeCN: piperidine-butylamine. The predominant reaction in all cases is nucleophilic displacement at the aryl carbon to give the arylamines (III), accompanied by an SN2 attack at the alkyl carbon when sec. amines are the nucleophiles to give phenol (IV) (mechanism; products are determined spectrophotometrically, no yields given).

Mechanistic studies in strong acids. 15. 4-[(3,4-Dimethoxyphenyl)azo]pyridine: two different pathways in the acid hydrolysis of the two methoxy groups

“…The concentrations of guests were so chosen as to meet the Benesi-Hildebrand conditions ([guest],/[host], > 10; t = total) and cover a range of 10-90% (mostly 40-80%) complexation. The actual titration data for selected guests are as follows, [guest], mM (0, mdeg): 20 (0.66), 25 (0.71), 30 (0.77), 40 (0.89), 50 (0.93) for (5,S)-2; 20 (1.19), 30 (1.33), 40 (1.54), 50 (1.63), 67 (1.71) for (S)-8; 2 (0.46), 4 (0.58), 6 (0.63), 8 (0.66), 10 (0.69), 16 (0.72), 20 (0.73) for 11; 10 (5.43), 12 (5.90), 15 (6.47), 20 (7.86), 30 (9.29), 40 (10.14) for 14; 10 (2.18), 12 (2.66), 14 (3.19), 20 (4.20), 25 (5.19), 40 (6.86), 50 (8.43), 80 (11.00). In every case, the Benesi-Hildebrand plots of [1],//1000 vs 1/[guest], according to eq 2 gave a straight line with r (correlation coefficient) > 0.98.…”