Simple descriptors for assessing the outcome of aza-Diels–Alder reactions

Abstract

The iminium aza-Diels-Alder (iADA) reaction of cyclopentadiene with 16 protonated alkyl alkylimineglyoxilates was studied using density functional theory (DFT) in order to elucidate how different substitution patterns in the dienophile may affect the reaction's outcome. Additionally, the application of the polarisable continuum model (PCM) together with the evaluation of the thermodynamic properties at different temperatures further allowed the surveying of the importance of such factors. These effects were combined into linear models which use the temperature, Taft's constants and characteristics of the solvent as descriptors for modelling and predicting the activation enthalpy and enthalpic balance of the iADA reactions under study. This model performs in a satisfactory manner, providing a cross-validation of the DFT framework traditionally used for predicting the outcome of these reactions and also uncovering novel insights into how the substitution patterns in the dienophile, the solvent and the temperature interact in order to give the characteristic regio-and stereoselectivity of the iADA reaction. Moreover, the results show that Taft's polar and steric substituent constants are important descriptors for assessing the outcome of iADA reactions.

Improving Vibrational Mode Interpretation Using Bayesian Regression

“…At the same time, νC (1) N (2) only accounts for 6.0% of ξ TS , on average. These results are in good accordance with the previous observations that this category ADA reactions are concerted, asynchronous cycloadditions. , …”

“…The fourth and fifth study cases under reported in this work explored the application of VMARD as a way to characterize the motion along the reaction coordinate of the oxygen-transfer step in vanadium-catalyzed epoxidations, and also on different aza-Diels–Alder condensations. Both these studies relied on the data generated in previous studies by the authors. , …”

“…Indeed, vibrational spectroscopic techniques, such as Fourier transform infrared (FTIR) and Raman spectroscopy permeate the chemical literature, providing valuable insights for the elucidation of molecular structures, , the organization of molecular clusters, − the role on interion interactions in ionic liquids, , as well as insights on the organization of novel nanostructured materials. − In latter years, theoretical predictions became essential tools, aiding in the interpretation of IR and Raman spectra . In addition to the aforementioned applications, theoretical predictions are a valuable aid in identifying the product of chemical reactions out of several possible outcomes, − and also allow the calculation of the thermodynamic and kinetic parameters of these reactions. − …”

Halogenation Thermodynamics of Pyrrolidinium-Based Ionic Liquids

“…Many similar correlations can be found using Tables – and Figure , which are left as an exercise for an interested reader. Alternative descriptors can also be systematically tested, for instance, Taft’s polar and steric substituent constants, as exemplified in the recent study of aza-Diels–Alder reactions …”

“…Alternative descriptors can also be systematically tested, for instance, Taft's polar and steric substituent constants, as exemplified in the recent study of aza-Diels−Alder reactions. 44 ■ CONCLUDING REMARKS Thermodynamics of fluorination, chlorination, and bromination is reported and discussed. It was found that halogenation of the N-ethyl-N-methylpyrrolidinium, N-ethylpyrrolidinium, and protonated pyrrolidine cations is thermodynamically allowed in almost all cases.…”