Ambient-Temperature Synthesis of Primary Amines via Reductive Amination of Carbonyl Compounds

Abstract

Efficient synthesis of primary amines via low-temperature reductive amination of carbonyl compounds using NH3 and H2 as the nitrogen and hydrogen resources is highly desired and challenging in the chemistry community. Herein, we employed naturally occurring phytic acid as a renewable precursor to fabricate titanium phosphate (TiP)-supported Ru nanocatalysts with different reduction degrees of RuO2 (Ru/TiP-x, x represents the reduction temperature) by combining ball milling and molten-salt processes. Very interestingly, the obtained Ru/TiP-100 had good catalytic performance for the reductive amination of carbonyl compounds at ambient temperature, resulting from the synergistic cooperation of the support (TiP) and the Ru/RuO2 with a suitable proportion of Ru0 (52%). Various carbonyl compounds could be efficiently converted into the corresponding primary amines with high yields. More importantly, the conversion of other substrates with reducible groups could also be achieved at ambient temperature. Detailed investigations indicated that the partially reduced Ru and the support (TiP) were indispensable. The high activity and selectivity of Ru/TiP-100 catalyst originates from the relatively high acidity and the suitable electron density of metallic Ru0.

Advances in the Catalytic Reductive Amination of Furfural to Furfural Amine: The Momentous Role of Active Metal Sites

“…However, this is in sharp contrast with the study related to Ru/TiP. [38] The absence of acidic sites in the case of MgO could also be another factor for its inactivity compared to Ru/TiP, which along with basic sites, has a comparatively more significant number of acidic sites.…”

“…In connection with the study mentioned above, Xie et al [38] investigated the influence of reduction temperature on RuO 2 / titanium phosphate (TiP) activity for the reductive amination of cyclohexanone at ambient temperature. RuO 2 /TiP-100 (reduced at 100 °C, having a reduction degree of 52 % RuO 2 ) displayed higher catalytic activity in terms of cyclohexylamine (97 %) than RuO 2 /TiP-80 (reduced at 80 °C, having a reduction degree of 44 % of RuO 2 ) (10 % cyclohexylamine) in methanol at 30 °C, 1.4 MPa H 2 , and 0.6 MPa NH 3 .…”

“…[54] On the other hand, Ru/TiP required ambient temperature (30 °C) to achieve an FUA yield of about 91 % due to having electron-donating support, facilitating the generation of easily reducible Ru species, and exhibited good recyclability of up to five runs. [38] As the pioneering work of recognizing the role of specific morphology on the catalytic activity of metal nanoparticles, [54] metal(s) on conventional spherical support having less active species, [52] and in continuation to the previous studies where electronic states of Ru were responsible for catalytic activity, [27,36,38] the activity of Ru on Nb 2 O 5 with various morphologies, such as Nb 2 O 5 -L(layer), Nb 2 O 5 -H(spherical), and Nb 2 O 5 -F(nanoslice-like) was investigated for the reductive amination of cyclopentanone. [58] CO-DRIFTS and XPS studies disclosed that these three catalysts possessed a large and small fraction of Ru n + and Ru 0 , respectively.…”

One-pot production of phenazine from lignin-derived catechol

“…From this, the whole conversion starts with the hydrogenation of catechol into 2-hydroxyl-cyclohexanone which is subsequently aminated to hydrogenated phzs . Since ketones easily react with ammonia to form imines, 53,60 2-hydroxyl-cyclohexylimine is likely to be the intermediate for 8H-phz formation. α-Hydroxyl-imine is more reactive than normal imines as it is easily isomerized into 2-amino-cyclohexanone via an Amadori (or Heyns) rearrangement.…”

Biosynthesis of Chiral Amino Alcohols via an Engineered Amine Dehydrogenase in E. coli

“…Direct asymmetric reductive amination of ketones with free ammonia to produce chiral amino alcohols is a highly aspirational transformation ( Abrahamson et al, 2013 ; Pushpanath et al, 2017 ). In the traditional chemical synthesis, it mainly relies on stoichiometric amounts of chemical reducing agents or organometallic catalysts, which are limited by low stereoselectivities, the formation of the alcohol as side product, and the requirement of extreme reaction conditions ( Larrow et al, 1996 ; Breuer et al, 2004 ; Ma et al, 2010 ; Nugent and El-Shazly, 2010 ; Karjalainen and Koskinen, 2012 ; Xie et al, 2020 ; Hollmann et al, 2021 ). Alternatively, enzymes as catalysts are increasingly explored as essential tools in asymmetric reductive aminations ( Reetz, 2011 ; Abrahamson et al, 2013 ; Schrittwieser et al, 2015 ; Chen and Arnold, 2020 ; Winkler et al, 2021 ).…”