In this work, three speculative mechanisms of the reaction between triphenylphosphine and dimethyl acetylendicarboxylate in the presence of 3‐chloropentane‐2,4‐dione were energetically and thermodynamically developed using quantum mechanical calculations and were profoundly compared with stopped‐flow and UV spectrophotometry approaches. The third speculative mechanism that led to the five‐membered ring structure was experimentally and theoretically favorable. The five‐membered ring structure of product was characterized by X‐ray crystallographic data. Also, steps 1 and 2 of the third mechanism were determined as fast and rate‐determining steps, respectively. The experimental kinetic evidence of the formation and decay of intermediate in steps 1 and 2 (fast and rate‐determining steps, respectively) was compatible with theoretical data. Experimental kinetic data were recognized for overall reaction along with activation parameters for fast and rate‐determining steps of the reaction. Theoretical kinetic data (k and Ea) and activation parameters (ΔG≠, ΔS,≠ and ΔH≠) were calculated for each step and overall reactions.

Modern society is dependent on synthetic chromene derivatives for use as drugs, including anticancer drugs, and for their biological activities.

The kinetics of the reaction between para-substituted anilines and dimethyl acetylenedicarboxylate (DMAD) with derivatives of benzaldehyde for the one-pot formation of 3,4,5-substituted furan-2(5H)-ones in the presence of lactic acid as a catalyst have been studied spectrophotometrically at different temperatures. A mechanism involving four steps was proposed for the reactions, all of which followed second-order kinetics. The partial orders with respect to substituted aniline and DMAD were one and one and the reactions revealed zeroorder kinetics for benzaldehyde and its derivatives. Changing of substituents on benzaldehyde left rates of reaction unaffected. However, various substituents on aniline showed that para electron-withdrawing groups decreased the rate of reaction. According to investigation of an isokinetic relationship, a common mechanism exists for all studied substituents and a general mechanism can be formulated. Kinetic values (k and E a) and associated activation parameters (ΔG ‡ , ΔS ‡ and ΔH ‡) of the reactions were determined.

No abstract

For the first time, theoretical calculations have been employed for assignment of the most stable isomers ([(2S*, 3S*) or (2R*, 3R*)] and [(2S*, 3R*) or (2R*, 3S*)] of a phosphonate ester containing 2-fluoroaniline at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) levels of theory. The results were showed that the compound with gauche arrangement and [(2S*, 3S*) or (2R*, 3R*)] configuration was more stable than the anti arrangement with [(2S*, 3R*) or (2R*, 3S*)] geometry. In addition, experimental 1H, 13C and 31P NMR data along with X-ray crystallographic data of the compound were consistent with the results obtained from theoretical calculations. Kinetic studies were performed on the reaction between triphenyl phosphite, dialkylacetylene dicarboxylates in the presence of an NH-acid, namely as 2-fluoroaniline (as a protic/nucleophilic reagent) for the generation of the compound with a gauche arrangement and [(2S*, 3S*) or (2R*, 3R*)] configuration. Kinetic data were obtained spectrophotometrically and a temperature study yielded activation parameters. A mechanistic scheme is proposed which fits all the kinetic data.