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.

Accelerated microdroplet synthesis of benzimidazoles by nucleophilic addition to protonated carboxylic acids

“…Examples of reactions known to be accelerated in the microdroplet environment include Suzuki coupling, 33 Fisher indole synthesis, 10 Katritzky transamination, 34 Claisen-Schmidt condensation, 35 Eschenmoser coupling, 35 Dakin reaction, 36 Baeyer-Villiger oxidation, 36 N-alkylation of indoles, 37 Combes reaction, 12 Pomeranz-Fritsch synthesis, 12 and cycloaddition reactions. 38 These microdroplet accelerated reactions can be performed under ambient conditions using nESI 10 or, in larger volumes, using electrosonic spray ionization (ESSI).…”

Effect of Droplet Size and Counterions on the Spatial Distribution of Ions

“…In Table 1 we have reported the range over which the integration is performed. The upper limit of integration is at the distance where the water density becomes 5 × 10 −4 g/cm 3 . In our simulations and in experimental set-ups a droplet may be surrounded by vapor.…”

“…Examples include dispersive liquidliquid micro-extraction, 1 micro-and nanofluidity and acceleration of reactions in electrosprayed droplets. [2][3][4][5][6][7] Even though our ability to carry out chemical reactions on mass-scale in these minute volumes is rapidly growing, the knowledge of the reaction mechanisms of the dissolved species in the droplet environment is still limited.…”

The Relation Between Ejection Mechanism and Ion Abundance in the Electric Double Layer of Drops

“…Multiple charged droplets are found in a number of highly diverse environments such as thunderclouds, 1 ink-jet printing, 2 mass spectrometry ionization methods, [3][4][5][6][7][8][9][10][11] and in the emerging area of aerosol micro-reactors. [12][13][14][15][16][17][18][19] The relation of the structure of a multiple charged droplet to the ion-ejection mechanisms has been a central question in mass spectrometry and atmospheric chemistry. The problem is significant because the (simple) ion-ejection may determine the charge state of macroions that are detected in native mass spectrometry.…”