Osmium Hydride Acetylacetonate Complexes and Their Application in Acceptorless Dehydrogenative Coupling of Alcohols and Amines and for the Dehydrogenation of Cyclic Amines

Abstract

The preparation of new osmium-hydride complexes, starting from OsH 6 (P i Pr 3) 2 (1) and OsH 2 Cl 2 (P i Pr 3) 2 (2), and their catalytic activity in acceptorless dehydrogenative coupling of alcohols and amines and in dehydrogenation of cyclic amines are reported. Complex 1 reacts with acetylacetone (Hacac) to give the classical trihydride OsH 3 (acac)(P i Pr 3) 2 (3). The protonation of 3 with triflic acid (HOTf) produces the release of H 2 and the formation of the unsaturated osmium(IV)-dihydride [OsH 2 (acac)(P i Pr 3) 2 ]OTf (4), which is also prepared starting from 2 via the intermediate OsH 2 Cl(acac)(P i Pr 3) 2 (5). Treatment of acetylacetone solutions of 5 with KOH affords Os(acac) 2 (P i Pr 3) 2 (6). In presence of 5 mol% of KOH, complexes 3-6 promote the coupling of benzylalcohol and aniline to give N-benzylideneaniline and H 2. Under the same conditions, complex 3 catalyzes a wide range of analogous couplings to afford a variety of imines, including aliphatic ones, with yields between 90 and 40% after 1-48 h. Complex 3 also catalyzes the dehydrogenation of cyclic amines. According to the amount of H 2 released by each gram of employed substrate, the amines have been classified into three classes: poor-(1,2,3,4-tetrahydroquinaldine, 2-methylindoline and 2,6dimethylpiperidine), moderate-(1,2,3,4-tetrahydroquinoline and 6-methyl-1,2,3,4-tetrahydroquinoline) and good-hydrogen donors (1,2,3,4-tetrahydroisoquinoline).

Osmium Catalysts for Acceptorless and Base-Free Dehydrogenation of Alcohols and Amines: Unusual Coordination Modes of a BPI Anion

“…This is in contrast with that previously observed for the acetylacetonate derivative OsH3(acac)(P i Pr3)2. 16 Under the same conditions, with this catalyst, 1,2,3,4-tetrahydroisoquinoline releases 1.50ꞏ10 -2 molꞏg -1 of H2, about 20% more than 1,2,3,4-tetrahydroquinoline (1.20ꞏ10 -2 molꞏg -1 ). A similar behavior has been observed for some ruthenium-hydride precursors.…”

“…One of them is located above the BMePI ligand, while the other one is situated below the anion. Thus, the coordination polyhedron around each osmium atom can be rationalized as a distorted octahedron with the arene occupying three sites of a face, whereas the pyridyl-imine unit (N(1)−Os(1)−N(2) = 61.17 16 4, N(2)−C(6) = 1.398 (6), N(2)−C(7) = 1.314 (6), N(3)−C(7) = 1.368 (6), N(3)−C(14) = 1.354 (6), N(4)−C(14) = 1.320 (6), N(4)−C(15) = 1.411 (6), N(1)−Os(1)−N(2) = 61.17 (16), N(5)−Os(2)−N(4) = 61.74 (16).…”

Manganese(III) Acetate Catalyzed Aerobic Dehydrogenation of Tertiary Indolines, Tetrahydroquinolines and an N‐Unsubstituted Indoline

“…Important contributions have been made in this field using heterogeneous [8] or welldefined homogeneous metal catalysts consisting of iridium, [9] ruthenium, [10] cobalt, [11] nickel, [12] iron, [13] and osmium compounds as well. [14] More recently, an acceptorless dehydrogenation of N-heterocycles using a well-defined Mn-PNP complex under basic conditions was also reported. [15] Despite these remarkable achievements made, the introduction of multi-step synthesized ligands, noble metal complexes, tedious catalysts preparation or harsh reaction conditions are major concerns, thus restricting their potential applications.…”

Dynamically Long-Term Imaging of Cellular RNA by Fluorescent Carbon Dots with Surface Isoquinoline Moieties and Amines

“…Next, compound 1 thermally dissociates into phenylenediamine and N 1 -(2-aminoethyl) - N 2 -ethylethane-1,2-diamine cation, and the latter attack the phenylenediamine ring preferentially in the electronically and sterically favored ortho position (compound 2 ) through Hofmann–Martius rearrangement . Then compound 2 transform to 3 as depicted in the literature and finally form isoquinoline-like moiety. , Interestingly, both amines and quinoline-like rings are also present in other RNA-specific dyes, such as ( E )-2-(2-(1H-indol-3-yl)­vinyl) quinaldine (E36), ( E )-2-(2,4,6-trimethoxystyryl) quinaldine (E144), ( E )-4-(2-(6-methoxy quinaldine-2-yl)­vinyl)- N , N -dimethylaniline (F22), and Styryl-TO (Table S1), implying that these structural features are critical for the specific binding and targeting of cellular RNA.…”