A Highly Active Catalyst for the Hydrogenation of Amides to Alcohols and Amines

Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine–ruthenium framework

“…The hydrogenation of ε-caprolactam ( 3h ), a cyclic amide which serves as the monomer of nylon-6, showed a similar pattern of C–N bond cleavage, giving amino alcohol 6h predominantly (azepane: 1%). For the hydrogenation of unactivated amide 3h , the catalytic activity of 1a (0.1 mol %) preactivated with a less amount of 2b was far superior to that of the Bergens’s catalyst 27 (TON = 970 with 1 mol % of 2b vs. 230 with 5 mol % of KN[Si(CH 3 ) 3 ] 2 under the identical conditions ( P H2  = 5 MPa, T  = 100 °C, t  = 24 h), giving 6h in 97% yield (Supplementary Table 1 for details). Products 6h and 6i are synthetic precursors of N , N -dimethyl-6-amino-1-hexanol, a polymerization initiator in polyurethane synthesis 49 .…”

“…1), which was used previously 38 as an additive for the preactivation of 2a in the absence of amide, was as effective as NaH for the amide hydrogenation catalyzed by 1a and 1b . Hydrogenation of three different, rather activated amides was also tested using 1a (0.01 or 0.1 mol %) preactivated with 2b or NaH (0.1 or 1 mol %) under H 2 pressure ( P H2(pre) ) = 1 or 8 MPa and temperature ( T pre ) = 160 °C, and the results were compared with those reported by Bergens 27 , in which [Ru(Ph 2 P(CH 2 ) 2 NH 2 ) 2 (η 3 -allyl)] + (BF 4 − ) was used with a larger amount of a base (4 mol % of KN[Si(CH 3 ) 3 ] 2 or 5 mol % of NaOCH 3 ) (Supplementary Table 1 for reaction conditions and comparison of hydrogenation results). Higher to comparable TON and TOF under identical hydrogenation conditions ( P H2  = 5 MPa, T  = 100 °C, t  = 24 h) were consistently shown by 1a in the hydrogenation of N , N -dimethylacetamide (TON = 530 vs. 500), N -phenylacetamide (TON = ~800 vs. 700), and N -phenyl-2-pyrrolidone (TON = 7700 vs. 7120) under more neutral p H .…”

Highly Chemoselective Reduction of Amides (Primary, Secondary, Tertiary) to Alcohols using SmI2/Amine/H2O under Mild Conditions

“…6 Ikariya 7 and Bergens 8 reported hydrogenation of activated secondary and tertiary amides/lactams using Ru catalysts at high temperatures and H 2 pressures (100 °C, 50 atm). Additionally, Enthaler and co-workers reported a bimetallic Mo complex for the catalytic hydrosilylation of N -aryl tertiary amides with good C–N scission chemoselectivity.…”

Hydrogenation of Polar Bonds Catalysed by Ruthenium-Pincer Complexes

“…9) showed that the bipyridyl-based Ru(II)-pincer complex (6) was a more effective catalyst than the pyridyl-based PNN-Ru(II) pincer complex (2). Later, other reports on the hydrogenation of amides to alcohols and amines were reported [34,[66][67][68].…”