TITLE:
Perfect Solvent- and Catalyst-Free Syntheses of Imine Derivatives Using the Pressure Reduction Technique
AUTHORS:
Shoko Suzuki, Hiroyuki Ito, Shinji Ishizuka, Risehiro Nonaka, Motoyoshi Noike, Takeshi Kodama, Kenji Funaki, Mizuho Taguchi, Taisei Kagaya, Sayaka Sato, Guillaume Redler, Yasuo Yokoyama
KEYWORDS:
Solvent-Free, Catalyst-Free, Neat Reaction, Pressure Reduction Technique, Imine
JOURNAL NAME:
Green and Sustainable Chemistry,
Vol.9 No.4,
October
12,
2019
ABSTRACT: In the field of organic syntheses, the development of environmentally
friendly methods based on the concept of green chemistry has been always
required. In response to this requirement, we reported solvent- and
catalyst-free syntheses of imines using the pressure reduction technique as a
key technology. We found that this reaction proceeded very rapidly in the
initial stage, but its rate decreased with the passage of time. It was also
found that the reaction of benzaldehyde with aniline had a specificity that the
phase transition occurred. In this method, the desired imines could be obtained
in good to excellent yields, but target compounds had to be given by
purifications using organic solvents. Therefore, we tried to develop the
perfect synthetic method of imine derivatives without organic or inorganic
solvents. We selected two methods and took them into this investigation. One
was exactly mixing (1:1, substance ratio) aldehydes and amines and the other
was employing lower pressure (>0.1 mmHg, previous method: 1.0 mmHg) at the
pressure reducing technique. When this improved synthetic method was performed,
it was revealed that pure target imines were obtained in excellent yields
without any purification.