Continuous flow synthesis of phenyl glucosazone and its conversion to 2H-1,2,3-Triazole building blocks

Abstract

A continuous flow approach for the generation of phenyl glucosazone from glucose and phenyl hydrazine is reported giving the pure target in 53% isolated yield. This thermal process generates the target product as an insoluble material that causes reactor fouling via adhering to the reactor walls. To overcome this issue a segmented flow approach was realised whereby streams of air and the reaction solution were combined in a T-piece and directed through the heated reactor coil. The resulting micro-mixing prevented reactor fouling and blocking and allowed for multi-hour reactions to generate the desired target in high yield. The value of the phenyl glucosazone product was demonstrated via its oxidative cyclisation into 2H-phenyl-1,2,3-triazoles which represent important heterocyclic scaffolds.

Ultrasonic or Microwave Modified Continuous Flow Chemistry for the Synthesis of Tetrahydrocannabinol: Observing Effects of Various Solvents and Acids

“…While microwave irradiation addresses kinetic problems when relatively narrow flow channels create solid phase/solution phase mixing problems, sonication addresses kinetic problems by producing cavitation bubbles, where high temperatures and pressures are experienced within the microenvironment of the cavitation bubbles produced. As the ultrasound intensity increases, the reaction rate increases due to an increase in the number of cavitation bubbles and an increase in the temperature within the cavitation bubbles as depicted in Figure a. − The traditional method of heating heats the reaction mixture outside in, which can cause uneven heating and inconsistent reaction kinetics with the need for stirring. The microwave radiation provides deeper penetration and heats the solvent and sample evenly while maintaining consistent reaction kinetics, as depicted in Figure b .…”

“…As the ultrasound intensity increases, the reaction rate increases due to an increase in the number of cavitation bubbles and an increase in the temperature within the cavitation bubbles as depicted in Figure 2 a. 16 − 18 The traditional method of heating heats the reaction mixture outside in, which can cause uneven heating and inconsistent reaction kinetics with the need for stirring. The microwave radiation provides deeper penetration and heats the solvent and sample evenly while maintaining consistent reaction kinetics, as depicted in Figure 2 b.…”