Accelerated Chemical Synthesis: Three Ways of Performing the Katritzky Transamination Reaction

Abstract

Typical laboratory exercises for undergraduate organic chemistry students involve bulk phase reactions with work up of product. In this study, students performed accelerated versions of the Katritzky reaction of para-substituted anilines with pyrylium salts in three ways: (i) by dropcasting reagents onto a paper surface and allowing solvent to evaporate, (ii) by evaporation of solvent from the reagent mixture in a rotary evaporator, and (iii) at an organic/water interface (“on water”). Students determined the reaction yield for all three accelerated reactions as well as in the conventional bulk phase by mass spectrometry. Acceleration factors (the ratio of the product to reagent ion signals in the accelerated vs conventional reaction) were used to compare the paper spray and rotary evaporator method as well as the “on water” method. Substituent effects were explored by using substituted anilines. Students’ understanding of acceleration of organic reactions was increased as seen in both laboratory reports and exit interviews.