On the application of the extended Fujita–Nishioka equation to polysubstituted systems. A kinetic study of the rearrangement of several poly-substituted Z-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazoles in dioxane/water

On the use of multi-parameter free energy relationships: the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole into (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas

“…Looking at the values of the various contributing susceptibility constants one can observe that the low (on this point see some our previous comments) 17a calculated r value (À1.25AE0.02) is strictly comparable to those previously obtained for both the relevant (Z)-arylhydrazones of series a (À1.29AE0.02) 14 and the meta-and parasubstituted (Z)-arylhydrazones of series c (À1.24AE0.02). 29 Of course a negative proximity polar constant (f À0.79AE0.05) and a positive proximity steric effect (d 0.45AE0.01) have been calculated: they are not very different from that obtained for the relevant (Z)-arylhydrazones of series a (f: À0.92AE0.05 and d: 0.52AE0.01, respectively).…”

“…Once more the log k A,R versus pS þ plots display quasi-unitary slopes over a wide pS þ range (see data in Table R of Supplementary data; average values: 0.912AE0.004 and À0.930AE0.009 in the baseand in the acid-catalyzed ranges, respectively, as expected for this kind of process carried out in water-like solvents), thus replicating the situations observed in the instances of 1ae38a (0.913, in the base-catalyzed range) 14 and of the meta-and para-substituted (Z)-arylhydrazones 19c, 20c, 22c, 24c, 26ce32c in both base-and acidcatalyzed paths. 28 Table 1 A summary of the FER application to the rearrangement of (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1ae38a) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole (1be38b) a Substrate FER b Pathway Substituents…”

On the use of multi-parameter free energy relationships: the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole into (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas

“…Looking at the values of the various contributing susceptibility constants one can observe that the low (on this point see some our previous comments) 17a calculated r value (À1.25AE0.02) is strictly comparable to those previously obtained for both the relevant (Z)-arylhydrazones of series a (À1.29AE0.02) 14 and the meta-and parasubstituted (Z)-arylhydrazones of series c (À1.24AE0.02). 29 Of course a negative proximity polar constant (f À0.79AE0.05) and a positive proximity steric effect (d 0.45AE0.01) have been calculated: they are not very different from that obtained for the relevant (Z)-arylhydrazones of series a (f: À0.92AE0.05 and d: 0.52AE0.01, respectively).…”

“…Once more the log k A,R versus pS þ plots display quasi-unitary slopes over a wide pS þ range (see data in Table R of Supplementary data; average values: 0.912AE0.004 and À0.930AE0.009 in the baseand in the acid-catalyzed ranges, respectively, as expected for this kind of process carried out in water-like solvents), thus replicating the situations observed in the instances of 1ae38a (0.913, in the base-catalyzed range) 14 and of the meta-and para-substituted (Z)-arylhydrazones 19c, 20c, 22c, 24c, 26ce32c in both base-and acidcatalyzed paths. 28 Table 1 A summary of the FER application to the rearrangement of (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1ae38a) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole (1be38b) a Substrate FER b Pathway Substituents…”

Can the Absence of Solvation of Neutral Reagents by Ionic Liquids Be Responsible for the High Reactivity in Base-Assisted Intramolecular Nucleophilic Substitutions in These Solvents?

“…As far as base effects are concerned, for the rearrangement of 1a in IL-1 (see data in Table ) only a small reactivity variation [at 298.1 K, ( k II ) BuA :( k II ) TEA :( k II ) PIP = 1:1.2:4.1] has been observed. In contrast, a much larger and a similar reactivity range were observed for 1b in PhH (at 313.1 K, 1:66:188) 9b and in ACN (at 283.1 K, 1:1.1:8.1),5f respectively. The effect of the reactivity-selectivity principle could, at least in part, account for the different behavior observed in the three solvents (PhH, ACN, and IL-1 ), but it must be remembered that in benzene, as well as in other conventional solvents, amine−solvent and amine−amine interactions could strongly differentiate the amines on the basis of their nature and of their steric requirements (both intrinsic, that is, structure-dependent and external, that is, dependent on amine−solvent interactions) unlike what probably occurs in IL-1 and ACN (see following).…”

Tuning the pKa of Fluorescent Rhodamine pH Probes through Substituent Effects

“…This result suggests that substituent effects in the Series 2 di‐ ortho compounds are much stronger than would be expected based on their mono‐ ortho counterparts and the assumption of additive effects. The extreme steric crowding in di‐ ortho ‐substituted aromatics has previously been shown to cause anomalously high reactivity compared to mono‐ ortho compounds in a kinetic study of Z‐arylhydrazones of oxadiazoles by Spisani and co‐workers . Here, the di‐ ortho ‐substituted compounds exhibit substituent effects on their p K a values that likewise exceed those expected by simple additivity.…”

On the use of multi-parameter free energy relationships: the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole into (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas

“…Looking at the values of the various contributing susceptibility constants one can observe that the low (on this point see some our previous comments) 17a calculated r value (À1.25AE0.02) is strictly comparable to those previously obtained for both the relevant (Z)-arylhydrazones of series a (À1.29AE0.02) 14 and the meta-and parasubstituted (Z)-arylhydrazones of series c (À1.24AE0.02). 29 Of course a negative proximity polar constant (f À0.79AE0.05) and a positive proximity steric effect (d 0.45AE0.01) have been calculated: they are not very different from that obtained for the relevant (Z)-arylhydrazones of series a (f: À0.92AE0.05 and d: 0.52AE0.01, respectively).…”

“…Once more the log k A,R versus pS þ plots display quasi-unitary slopes over a wide pS þ range (see data in Table R of Supplementary data; average values: 0.912AE0.004 and À0.930AE0.009 in the baseand in the acid-catalyzed ranges, respectively, as expected for this kind of process carried out in water-like solvents), thus replicating the situations observed in the instances of 1ae38a (0.913, in the base-catalyzed range) 14 and of the meta-and para-substituted (Z)-arylhydrazones 19c, 20c, 22c, 24c, 26ce32c in both base-and acidcatalyzed paths. 28 Table 1 A summary of the FER application to the rearrangement of (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1ae38a) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole (1be38b) a Substrate FER b Pathway Substituents…”

Can the Absence of Solvation of Neutral Reagents by Ionic Liquids Be Responsible for the High Reactivity in Base-Assisted Intramolecular Nucleophilic Substitutions in These Solvents?

“…As far as base effects are concerned, for the rearrangement of 1a in IL-1 (see data in Table ) only a small reactivity variation [at 298.1 K, ( k II ) BuA :( k II ) TEA :( k II ) PIP = 1:1.2:4.1] has been observed. In contrast, a much larger and a similar reactivity range were observed for 1b in PhH (at 313.1 K, 1:66:188) 9b and in ACN (at 283.1 K, 1:1.1:8.1),5f respectively. The effect of the reactivity-selectivity principle could, at least in part, account for the different behavior observed in the three solvents (PhH, ACN, and IL-1 ), but it must be remembered that in benzene, as well as in other conventional solvents, amine−solvent and amine−amine interactions could strongly differentiate the amines on the basis of their nature and of their steric requirements (both intrinsic, that is, structure-dependent and external, that is, dependent on amine−solvent interactions) unlike what probably occurs in IL-1 and ACN (see following).…”

Tuning the pKa of Fluorescent Rhodamine pH Probes through Substituent Effects

“…This result suggests that substituent effects in the Series 2 di‐ ortho compounds are much stronger than would be expected based on their mono‐ ortho counterparts and the assumption of additive effects. The extreme steric crowding in di‐ ortho ‐substituted aromatics has previously been shown to cause anomalously high reactivity compared to mono‐ ortho compounds in a kinetic study of Z‐arylhydrazones of oxadiazoles by Spisani and co‐workers . Here, the di‐ ortho ‐substituted compounds exhibit substituent effects on their p K a values that likewise exceed those expected by simple additivity.…”

On the use of multi-parameter free energy relationships: the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole into (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas

“…Looking at the values of the various contributing susceptibility constants one can observe that the low (on this point see some our previous comments) 17a calculated r value (À1.25AE0.02) is strictly comparable to those previously obtained for both the relevant (Z)-arylhydrazones of series a (À1.29AE0.02) 14 and the meta-and parasubstituted (Z)-arylhydrazones of series c (À1.24AE0.02). 29 Of course a negative proximity polar constant (f À0.79AE0.05) and a positive proximity steric effect (d 0.45AE0.01) have been calculated: they are not very different from that obtained for the relevant (Z)-arylhydrazones of series a (f: À0.92AE0.05 and d: 0.52AE0.01, respectively).…”

“…Once more the log k A,R versus pS þ plots display quasi-unitary slopes over a wide pS þ range (see data in Table R of Supplementary data; average values: 0.912AE0.004 and À0.930AE0.009 in the baseand in the acid-catalyzed ranges, respectively, as expected for this kind of process carried out in water-like solvents), thus replicating the situations observed in the instances of 1ae38a (0.913, in the base-catalyzed range) 14 and of the meta-and para-substituted (Z)-arylhydrazones 19c, 20c, 22c, 24c, 26ce32c in both base-and acidcatalyzed paths. 28 Table 1 A summary of the FER application to the rearrangement of (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1ae38a) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole (1be38b) a Substrate FER b Pathway Substituents…”

Can the Absence of Solvation of Neutral Reagents by Ionic Liquids Be Responsible for the High Reactivity in Base-Assisted Intramolecular Nucleophilic Substitutions in These Solvents?

“…As far as base effects are concerned, for the rearrangement of 1a in IL-1 (see data in Table ) only a small reactivity variation [at 298.1 K, ( k II ) BuA :( k II ) TEA :( k II ) PIP = 1:1.2:4.1] has been observed. In contrast, a much larger and a similar reactivity range were observed for 1b in PhH (at 313.1 K, 1:66:188) 9b and in ACN (at 283.1 K, 1:1.1:8.1),5f respectively. The effect of the reactivity-selectivity principle could, at least in part, account for the different behavior observed in the three solvents (PhH, ACN, and IL-1 ), but it must be remembered that in benzene, as well as in other conventional solvents, amine−solvent and amine−amine interactions could strongly differentiate the amines on the basis of their nature and of their steric requirements (both intrinsic, that is, structure-dependent and external, that is, dependent on amine−solvent interactions) unlike what probably occurs in IL-1 and ACN (see following).…”

Tuning the pKa of Fluorescent Rhodamine pH Probes through Substituent Effects

“…This result suggests that substituent effects in the Series 2 di‐ ortho compounds are much stronger than would be expected based on their mono‐ ortho counterparts and the assumption of additive effects. The extreme steric crowding in di‐ ortho ‐substituted aromatics has previously been shown to cause anomalously high reactivity compared to mono‐ ortho compounds in a kinetic study of Z‐arylhydrazones of oxadiazoles by Spisani and co‐workers . Here, the di‐ ortho ‐substituted compounds exhibit substituent effects on their p K a values that likewise exceed those expected by simple additivity.…”