TITLE:
Efficient Solvent- and Catalyst-Free Syntheses of Imine Derivatives Applying the Pressure Reduction Technique: Remarkable Change of the Reaction Rate with the Phase Transition
AUTHORS:
Shoko Suzuki, Shujiro Sakaki, Shinji Ishizuka, Tomomichi Nishino, Hiroyuki Ito, Risehiro Nonaka, Motoyoshi Noike, Takeshi Kodama, Hajime Nozaka, Tsuneyuki Sato, Hitoshi Agematsu, Koichi Maruyama, Shun Oyamada, Takashi Kuroishi, Kazuma Sasaki, Kei Yagawa, Mami Yoshioka, Yasuo Yokoyama
KEYWORDS:
Solvent-Free, Catalyst-Free, Pressure Reduction Technique, Imine, Reaction Rate, Phase Transition
JOURNAL NAME:
Green and Sustainable Chemistry,
Vol.8 No.2,
May
18,
2018
ABSTRACT: Because imines could be used as convenient starting materials in various fields, the development of an easy synthetic method of imine was strongly desired. In response to this demand, we thought that it would be an effective synthesis method if an aldehyde and an amine could be reacted to give an imine in good yield under solvent- and catalyst-free conditions. In fact, we tried the reaction of benzaldehyde with various amines under solvent- and catalyst-free conditions followed by removal of water that was produced in the reaction system by a vacuum pump, and desired imines could be obtained in good yields. Observation of this reaction using a nuclear magnetic resonance spectrometer revealed that the reaction rate was extremely fast at the initial stage but slowed over time. However, the reaction of benzaldehyde with aniline differed greatly, and the reaction rate dramatically improved in 47 - 48 minutes after the start of the reaction. At this time, we found that the reaction system underwent a phase transition from the liquid phase to the solid phase.