Kinetic studies of the reactions of aryl phenyl chlorothiophosphates (1) and aryl 4-chlorophenyl chlorothiophosphates (2) with substituted anilines in acetonitrile at 55.0 degrees C are reported. The negative values of the cross-interaction constant rhoXY (rhoXY = -0.22 and -0.50 for 1 and 2, respectively) between substituents in the nucleophile (X) and substrate (Y) indicate that the reactions proceed by concerted SN2 mechanism. The primary kinetic isotope effects (kH/kD = 1.11-1.13 and 1.10-1.46 for 1 and 2, respectively) involving deuterated aniline nucleophiles are obtained. Front- and back-side nucleophilic attack on the substrates is proposed mainly on the basis of the primary kinetic isotope effects. A hydrogen-bonded, four-center-type transition state is suggested for a front-side attack, while the trigonal bipyramidal pentacoordinate transition state is suggested for a back-side attack. The MO theoretical calculations of the model reactions of dimethyl chlorothiophosphate (1') and dimethyl chlorophosphate (3') with ammonia are carried out. Considering the specific solvation effect, the front-side nucleophilic attack can occur competitively with the back-side attack in the reaction of 1'.

The nucleophilic substitution reactions of Y-O-aryl phenyl phosphonochloridothioates with substituted anilines (XC 6 H 4 NH 2 ) and deuterated anilines (XC 6 H 4 ND 2 ) are kinetically investigated in acetonitrile at 55.0 o C. The deuterium kinetic isotope effects (DKIEs) invariably increase from an extremely large secondary inverse (k H /k D = 0.439; min) to a primary normal (k H /k D = 1.34; max) as both substituents of nucleophile (X) and substrate (Y) change from electron-donating to electron-withdrawing. These results are opposite to the DKIEs on Y-O-aryl methyl phosphonochloridothioates, and can be rationalized by the gradual transition state (TS) variation from backside to frontside attack. The trigonal bipyramidal pentacoordinate TS is proposed for a backside attack, while the hydrogen-bonded, four-center-type TS is proposed for a frontside attack. The negative values of the cross-interaction constants (ρ XY(H) = −0.38 for XC 6 H 4 NH 2 and ρ XY(D) = −0.29 for XC 6 H 4 ND 2 ) indicate that the reactions proceed by a concerted S N 2 mechanism.

The nucleophilic displacements at carbonyl center are remarkable. Mainly stepwise mechanism was found in these reactions. The stepwise mechanism with rate-limiting addition of the nucleophilie to the carbonyl group to form zwitterionic tetrahedral intermediate was a common type of mechanism. Such as, Dey et al. [1] proposed the pyridinolyses of α-chloroacetanilides proceed via a stepwise mechanism with rate-limiting addition of the nucleophile to the carbonyl group to form zwitterionic tetrahedral intermediate (T ±). In some cases concerted mechanism was found. Oh and coworkers [9] reported that a concerted mechanism with a hydrogen bonded cyclic transition state for the aminolysis of aryl N-allyl thiocarbamates with benzylamines in acetonitrile The mechanism change from stepwise to concerted was also found in some cases. It was concluded that the change of the amine from benzylamines to anilines causes a shift of the aminolysis mechanism from a concerted to a stepwise process. This paper includes an exclusive review of literature from 1997 to 2015.