Synthesis of Stable Phosphorus Ylides from 6-Chloro-2-Benzoxazolinone and Kinetic Investigation of the Reactions by Uv Spectrophotometry

Abstract

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reactions between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of an NH-acid, such as 6-chlorobenzoxazolinone. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometry. The second order fits were drawn and the values of the second order rate constant (k2) were calculated automatically using standard equations within the program. Over the temperature range studied, the dependence of the second order rate constant (Ln k2) on reciprocal temperature was in a good agreement with the Arrhenius equation, leading to the activation energies of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, the structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also the concentration of reactants on the rate of reactions. The proposed mechanism is consistent with the results obtained and the steady state approximation, and the first step (k2) of reaction was recognized as the rate-determining step on the basis of experimental data.

A Mechanistic Investigation of Stable Phosphonate Ester Derived from 3, 4 dichloro Aniline: A Kinetics Study and Theoretical Calculations

“…In fact, in recent works triphenyl phosphite has been used instead of triphenylphosphine in the previous work. [33][34][35][36][37][38][39][40][41] In addition, the product is phosphonate esters 4 not phosphorus ylides. Synthesis of compounds 4, shown in Figure 1, has been reported earlier.…”

Theoretical, Kinetic and Mechanistic Studies of the Reaction between Dialkyl Acetylenedicarboxylates, Triphenylphosphine and Pyrrole in Organic Solvents

“…These ylides usually exist as a mixture of the two geometrical isomers (Z-and E-), although some exhibit only one isomer. Kinetic investigations of the equilibrium interchange process between the Z-and E-isomers in stable phosphorus ylides have undertaken experimentally [17 -20] and quantum mechanical calculations have confirmed these results [21,22]. We have previously reported the kinetics and mechanism of several phosphorus ylides [23 -27].…”

Kinetic and Mechanistic Investigation of Pyrano[2,3-d]pyrimidine Formation in the Presence of Catalyst under Novel One-Pot Three-Component Reaction

“…Kinetics and mechanism of numerous reactions have been previously studied using the UV-vis technique [24][25][26][27][28]. In recent years, we have endeavored to expand the synthesis of phosphorous ylides along with developing experimental and theoretical studies on the kinetics and mechanisms of these reactions [29][30][31][32][33][34][35][36]. In these studies, reactions occurred by at least three steps.…”

“…Moreover, the overall reaction order followed second-order kinetics. The rate of all reactions was increased in solvents with upper dielectric constant value that could be related to the differences in stabilization of the reactants and the zwitterionic intermediate by the solvents [29][30][31][32][33][34][35][36]. In present work, we describe kinetic results together with detailed mechanistic studies for the one-pot, three-component condensation reactions consisting of 4-nitrobenzaldehyde 2, malononitrile 3, and thiobarbituric acid 1 in the presence of sodium acetate as a catalystin methanol and environmental friendless solvents (mixture of ethanol and H 2 O 50/50) based on a global kinetic analysis methodology using the UV-vis spectrophotometry apparatus.…”