A Domino Fusion of an Organic Ligand Depended on Metal‐Induced and Oxygen Insertion, Unraveled by Crystallography, Mass Spectrometry, and DFT Calculations

Abstract

Herein, the reaction of (1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)methanamine (L1) with Co(H2O)6Cl2, in CH3CN at 120 °C, leading to the 2,3,5,6‐tetrakis(1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)pyrazine (3), isolated as a dimeric cluster {[CoII2(3)Cl4]⋅2 CH3CN} (2), is reported. When O2 and H2O are present, (1‐methyl‐1 H‐benzo[d]imidazole‐2‐carbonyl)amide (HL1′) is first formed and crystallized as [CoIII(L1)2(L1′)]Cl2⋅2 H2O (4) before fusion of HL1′ with L1, giving 1‐methyl‐N‐(1‐methyl‐1 H‐benzo[d]imidazol‐2‐carbonyl)‐1 H‐benzo[d]imidazol‐2‐carboxamide (HL2′′) forming a one‐dimensional (1D) chain of [CoII3(L2′′)2Cl4]n (5). The combination of crystallography and mass spectrometry (ESI‐MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2, but six steps for 5, for which a different sequence takes place. Control and isotope labeling experiments confirm the two carbonyl oxygen atoms in 5 originate from both air and water. The dependence on the metals, compared with FeCl3⋅6 H2O leading to a stable triheteroarylmethyl radical, is quite astounding, which could be attributed to the different oxidation states of the metals and coordination modes confirmed by DFT calculations. This metal and valence dependent process is a very useful way for selectively obtaining these large molecules, which are unachievable by common organic synthesis.

Tracking the Process of Domino Ring‐Opening and Coupling of Fused Imidazole and Direct Observation of Peroxide Intermediates

“…[ 14 ] A domino amine oxidative self‐coupling and formal [3+3] cycloaddition mechanism is proposed to produce the substituted pyrazine derivative L4 (2,3,5,6‐tetrakis(1‐methyl‐1 H‐ benzo[ d ]imidazol‐2‐yl)pyrazine) from L1 (1‐methyl‐1 H‐ benzo[ d ]imidazol‐ 2‐yl)methanamine (Table S4). [ 15 ] A rare solvothermal domino reaction with up to 14 steps to give a stable triheteroarylmethyl radical L6 ((tris(4‐methyl‐1‐(1‐methyl‐1 H‐ benzo[ d ]imidazol‐2‐yl)‐ 4 H‐ benzo[ d ]imidazo[1,5‐ a ]imidazole‐3‐yl)methyl hydrochloride)) from L1 has also been developed (Table S4). [ 7 ]…”

Mn(II) Promoted Divergent‐Convergent Domino Reaction Giving Dinuclear Tetrasubstituted Pyrrole Complex

“…Our group has developed a series of domino reactions between 3d transition metal salts and chelating substrates containing active groups such as amino and hydroxyl groups. [13,14] We have found that the types of the coordinating atoms and the heteroaryl groups have great influences on reaction sequence. Recently, we have developed a domino reaction between CoCl 2 • 6H 2 O and L1 (1-methyl-1Hbenzo[d]imidazol-2-yl)methanamine), which produced the 2,3,5,6-tetrakis(1-methyl-1H-benzo[d]imidazol-2-yl)pyrazine [13] (L4) (Scheme 1, (1) ).…”

“…[13,14] We have found that the types of the coordinating atoms and the heteroaryl groups have great influences on reaction sequence. Recently, we have developed a domino reaction between CoCl 2 • 6H 2 O and L1 (1-methyl-1Hbenzo[d]imidazol-2-yl)methanamine), which produced the 2,3,5,6-tetrakis(1-methyl-1H-benzo[d]imidazol-2-yl)pyrazine [13] (L4) (Scheme 1, (1) ). The possible reaction pathway has been proposed and the coordination between Co 2 + and L1 could not only activate the terminal amine group for self-condensation to give imine intermediate (Int 1) but also facilitate the subsequent formal [3 + 3] cycloaddition of Int 1 to give the pyrazine ring.…”

Hydrazine–Halogen Exchange Strategy Toward N═N-Containing Compounds and Process Tracking for Mechanistic Insight

“…To date, many reports on Cu-catalyzed C–N coupling of N-sources with cyclic iodoniums are mechanistically ambiguous, with no experimental evidence for the described Cu intermediates therein. Our research group has developed a strategy to track the overall progress of complex reactions through time-dependent electrospray ionization mass spectrometry (TD ESI-MS), which can give detailed information on the chemical species at different reaction times . In this paper, through TD ESI-MS, the generation, development, and termination of all the intermediates including six Cu complexes are characterized, giving sufficient evidence for the mechanism of current transformation.…”