Aminolysis of Y-Substituted Phenyl Diphenylphosphinates and Benzoates:  Effect of Modification of Electrophilic Center from CO to PO

Abstract

The effect of modification of the electrophilic center from C=O to P=O on reactivity and reaction mechanism has been investigated for aminolysis of Y-substituted phenyl diphenylphosphinates (1a-j) and benzoates (2a-i). The phosphinates 1a-j are less reactive than the benzoates 2a-i. The reactions of 2,4-dinitrophenyl diphenylphosphinate (1a) with alicyclic secondary amines resulted in a linear Brønsted-type plot with a beta(nuc) value of 0.38, while the corresponding reactions of 2,4-dinitrophenyl benzoate (2a) yielded a curved Brønsted-type plot. Similarly, a linear Brønsted-type plot with a beta(lg) value of -0.66 was obtained for the reactions of 1a-j with piperidine, while the corresponding reactions of 2a-i gave a curved Brønsted-type plot. The linear Brønsted-type plots for the reactions of 1a-j have been taken as evidence for a concerted mechanism, while the curved Brønsted-type plots for the reactions of 2a-i have been suggested to indicate a change in the rate-determining step of a stepwise mechanism. The Hammett plot for the reactions of 1b-j exhibited a poor correlation with sigma(-) constants (R(2) = 0.962) but slightly better correlation with sigma(o) (R(2) = 0.986). However, the Yukawa-Tsuno plot for the same reactions resulted in an excellent correlation (R(2) = 0.9993) with an r value of 0.30. The aminolysis of 1a-j has been suggested to proceed through a concerted mechanism with an early transition state on the basis of the small beta(nuc) and small r values.

Nucleophilic substitution reactions of diethyl 4‐nitrophenyl phosphate triester: Kinetics and mechanism

“…The value of the Brønsted slope obtained in the SA aminolysis of 1 (β = 0.39 ± 0.02, R 2 = 0.99) is in agreement with those found in the concerted reactions of 4-nitrophenyl diphenylphosphinate with SA amines in DMSO-H 2 O 20:80 mol% (β = 0.38) [15,16] and the concerted pyridinolyses of methyl S-aryl thiophosphate and methyl aryl phosphate diesters in the same solvent mixture, β = 0.42 and 0.56, respectively [17].…”

Kinetic Study on Reactions of O‐Y‐substituted Phenyl Thionobenzoates with Quinuclidine: Factors Governing Reactivity and Reaction Mechanism

“…Nucleophilic substitution reactions of esters with amines have intensively been investigated due to their importance in biological processes as well as in synthetic applications . Aminolysis of esters has been reported to proceed through a concerted mechanism or via a stepwise pathway depending on reaction conditions ( e.g ., nature of the electrophilic center, amines, and reaction medium) . Reactions of 2,4‐dinitrophenyl diphenylphosphinate ( 1 ) with primary and secondary amines have been reported to proceed through a concerted mechanism on the basis of a linear Brønsted‐type plot with β nuc = −0.4 ± 0.1 .…”

Mechanism of the aminolysis of dimethyl phenylphosphinate: A DFT study

“…Aminolysis of phosphates and phosphinates has been investigated by kinetic studies [11][12][13][14]. Cook et al investigated the aminolysis of aryl diphenylphosphinates and related compounds in acetonitrile.…”

“…Lee et al studied the pyridinolysis of phenyl-substituted phenyl chlorophosphates in acetonitrile and proposed a concerted mechanism [12]. Um et al performed kinetic studies on aminolysis of aryl diphenylphosphinates and concluded that the reactions proceeded through a concerted mechanism [13]. They also extended their study to aminolysis of aryl diphenylphosphinothioates to investigate the effect of modification of the electrophilic center from P@O to P@S on reactivity and reaction mechanisms [14].…”