Buback, M.; Tost, W.; Tietze, L. F.; Voß, E.
Inter- and Intramolecular hetero Diels-Alder Reactions, XXII. Hetero Diels-Alder Reactions of Enamine Carbaldehydes at High Pressure Studied by On-Line IR Detection
Chem. Ber. 1988, 121, 781-785.
 

The hetero Diels-Alder reaction of 1 and 2 to the 4-aminodihydropyrans 3 and 4 in CH₂Cl₂ and isodurene solutions is studied between 45 °C and 95 °C by direct quantitative infrared spectroscopy under high pressure up to 3 kbar. The activation energies in isodurene and in CH₂Cl₂ are found to be 65 ± 5 kJ · mol^-1, and 58 ± 9 kJ · mol^-1, respectively. The activation volumes turn out to be practically identical: -25.1 ± 1.7 cm³ · mol^-1 in CH₂Cl₂ and -25.0 ± 1.8 cm³ · mol^-1 in isodurene. The promising aspects of applying high-pressure infrared spectroscopy to the detailed kinetic study of organic reactions are indicated.