58114-25-3Relevant articles and documents
La[N(sime3)2]3-catalyzed deoxygenative reduction of amides with pinacolborane. scope and mechanism
Barger, Christopher J.,Dicken, Rachel D.,Weidner, Victoria L.,Motta, Alessandro,Lohr, Tracy L.,Marks, Tobin J.
supporting information, p. 8019 - 8028 (2020/05/27)
Tris[N,N-bis(trimethylsilyl)amide]lanthanum (LaNTMS) is an efficient and selective homogeneous catalyst for the deoxygenative reduction of tertiary and secondary amides with pinacolborane (HBpin) at mild temperatures (25-60 °C). The reaction, which yields amines and O(Bpin)2, tolerates nitro, halide, and amino functional groups well, and this amide reduction is completely selective, with the exclusion of both competing inter- and intramolecular alkene/alkyne hydroboration. Kinetic studies indicate that amide reduction obeys an unusual mixed-order rate law which is proposed to originate from saturation of the catalyst complex with HBpin. Kinetic and thermodynamic studies, isotopic labeling, and DFT calculations using energetic span analysis suggest the role of a [(Me3Si)2N]2La-OCHR(NR′2)[HBpin] active catalyst, and hydride transfer is proposed to be ligand-centered. These results add to the growing list of transformations that commercially available LaNTMS is competent to catalyze, further underscoring the value and versatility of lanthanide complexes in homogeneous catalysis.
Aluminium complex as an efficient catalyst for the chemo-selective reduction of amides to amines
Das, Suman,Karmakar, Himadri,Bhattacharjee, Jayeeta,Panda, Tarun K.
, p. 11978 - 11984 (2019/08/13)
We report an efficient protocol for the catalytic chemo-selective reduction of tert-amides with pinacolborane (HBpin) to afford the corresponding amines in high yields using aluminium complexes [κ2-{Ph2P(X)NC9H6N}Al(Me)2] [X = S (2a), Se (2b)] as pre-catalysts at room temperature. The aluminium complexes were prepared from the reaction of [Ph2P(X)NC9H6N] [X = S (1a), Se (1b)] and trimethylaluminium in toluene. The solid-state structure of complex 2b is established. Tertiary amides with a wide array of electron-withdrawing and electron-donating functional groups were easily converted to the desired products through the selective cleavage of the amides' CO bond by aluminium hydride as an active species. A kinetic study of the catalytic reaction is also reported.
Magnesium-catalyzed mild reduction of tertiary and secondary amides to amines
Lampland, Nicole L.,Hovey, Megan,Mukherjee, Debabrata,Sadow, Aaron D.
, p. 4219 - 4226 (2015/11/11)
The first example of a catalytic hydroboration of amides for their deoxygenation to amines is reported. This transformation employs an earth-abundant magnesium-based catalyst. Tertiary and secondary amides are reduced to amines at room temperature in the presence of pinacolborane (HBpin) and catalytic amounts of ToMMgMe (ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). Catalyst initiation and speciation is complex in this system, as revealed by the effects of concentration and order of addition of the substrate and HBpin in the catalytic experiments. ToMMgH2Bpin, formed from ToMMgMe and HBpin, is ruled out as a possible catalytically relevant species by its reaction with N,N-dimethylbenzamide, which gives Me2NBpin and PhBpin through C-N and C-C bond cleavage pathways, respectively. In that reaction, the catalytic product benzyldimethylamine is formed in only low yield. Alternatively, the reaction of ToMMgMe and N,N-dimethylbenzamide slowly gives decomposition of ToMMgMe over 24 h, and this interaction is also ruled out as a catalytically relevant step. Together, these data suggest that catalytic activation of ToMMgMe requires both HBpin and amide, and ToMMgH2Bpin is not a catalytic intermediate. With information on catalyst activation in hand, tertiary amides are selectively reduced to amines in good yield when catalytic amounts of ToMMgMe are added to a mixture of amide and excess HBpin. In addition, secondary amides are reduced in the presence of 10 mol % ToMMgMe and 4 equiv of HBpin. Functional groups such as cyano, nitro, and azo remain intact under the mild reaction conditions. In addition, kinetic experiments and competition experiments indicate that B-H addition to amide C-O is fast, even faster than addition to ester C=O, and requires participation of the catalyst, whereas the turnover-limiting step of the catalyst is deoxygenation.
