Titanium‐Mediated Catalytic Hydrogenation of Monocyclic and Polycyclic Arenes

Gómez‐Torres, Alejandra; Aguilar‐Calderón, J. Rolando; Encerrado-Manriquez, Angela M.; Pink, Maren; Metta‐Magaña, Alejandro J.; Lee, Wen‐Yee; Fortier, Skye

doi:10.1002/chem.201905466

Cited by 18 publications

(16 citation statements)

References 30 publications

(38 reference statements)

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“…The Ti–Ti distances (avg., 3.07 Å) in 2 are significantly elongated than in 1 ·1.5C 7 H 8 , while exhibiting inequivalent Ti–N Im bridging distances with average lengths of 1.98 and 2.17 Å. Subtle structural changes between the two polymorphs do exist, namely the titanium bonded η 6 -aryl ring in 2 - Pccn exhibits a boat conformation where the ipso and para carbon atoms deviate from the ring plane by 11° and 5°, respectively, whereas the masking aryl substituent in 2 - P 1̅ adopts a puckered ring, similar to that found in A and B , with an average fold angle of 12.6°, slightly larger than the 10° of A . However, the ring fold in 2 - P 1̅ falls along an ortho / meta carbon atom vector, unique from the ipso / para carbon atom fold planes of A and B .…”

Section: Results and Discussionmentioning

confidence: 87%

“…In recent years, impressive strides have been made in the development of the low-valent chemistry of the early metals (electron counts ≥ d 2 ), showing these systems to be formidable reductants capable of small molecule activation that can also mediate important organic chemistries. − In our own laboratory, we have shown that the reduced arene-masked titanium complexes ( Arket guan)Ti(η 6 -NIm Dipp ) ( Arket guan = [( t Bu 2 CN)C(NAr) 2 ] − , Ar = C 6 H 3 -2,6- i Pr 2 ( A ), C 6 H 3 -3,5-Me 2 ( B ); Im Dipp N = [1,3-bis(Dipp)imidazolin-2-iminato] − , Dipp = C 6 H 3 -2,6- i Pr 2 ) (Chart ) can perform the catalytic hydrogenation of mono- and polycyclic aromatic hydrocarbons as well as accomplish the hydrodesulfurization (HDS) of thiophene. − The latter example is particularly noteworthy, as the titanium complex shows a very rare display of fully reversible, early metal oxidative-addition/reductive-elimination during the initial HDS step involving ring opening of the thiophene. Nevertheless, these chemistries are limited to two-electron redox cycling.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric “Ti(I)” and “Ti(0)” Synthons Supported by Imidazolin-2-Iminato Ligands

et al. 2022

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Reduction of the diamagnetic Ti(III)/Ti(III) dimer [Cl 2 Ti(μ-NIm Dipp )] 2 (1) (NIm Dipp = [1,3-bis(Dipp)imidazolin-2-iminato] − , Dipp = C 6 H 3 -2,6-i Pr 2 ) with 4 and 6 equiv of KC 8 generates the intramolecularly arene-masked, dinuclear titanium compounds [(μ-Nη 6 -Im Dipp )Ti] 2 (2) and {[(Et 2 O) 2 K](μ-N-μ-η 6 :η 6 -Im Dipp )Ti} 2 (3), respectively, in modest yields. The compounds have been structurally characterized by X-ray crystallographic analysis, and inspection of the bond metrics within the η 6 -coordinated aryl substituent of the bridging imidazolin-2-iminato ligand shows perturbation of the aromatic system most consistent with two-electron reduction of the ring. As such, 2 and 3 can be assigned respectively as possessing metal centers in formal Ti(III)/Ti(III) and Ti(II)/Ti(II) oxidation states. Exploration of their redox chemistry reveal the ability to reduce several substrate equivalents. For instance, treatment of 2 with excess C 8 H 8 (COT) forms the novel COTbridged complex [(Im Dipp N)(η 8 -COT)Ti](μ-η 2 :η 3 -COT)[Ti(η 4 -COT)(NIm Dipp )] (4) that dissociates in THF solutions to give mononuclear (Im Dipp N)Ti(η 8 -COT)(THF) (5). Addition of COT to 3 yields heterometallic [(Im Dipp N)(η 4 -COT)Ti(μ-η 4 :η 5 -COT)K(THF)-(μ-η 6 :η 4 -COT)Ti(NIm Dipp )(μ-η 4 :η 4 -COT)K(THF) 2 ] n (6). Compounds 4 and 5 are the products of the 4-electron oxidation of 2, while 6 stands as the 8-electron oxidation product of 3. Reduction of organozides was also explored. Low temperature reaction of 2 with 4 equiv of AdN 3 gives the terminal and bridged imido complex [(Im Dipp N)Ti(�NAd)](μ-NAd) 2 [Ti(NIm Dipp )(N 3 Ad)] (7) that undergoes intermolecular C−H activation of toluene at room temperature to afford the amido compound [(Im Dipp N)Ti-(NHAd)](μ-NAd) 2 [Ti(C 6 H 4 Me)(NIm Dipp )] (8-tol). These complexes are the 6-electron oxidation products of the reaction of 2 with AdN 3 . Furthermore, treatment of 3 with 4 equiv of AdN 3 produces the thermally stable Ti(III)/Ti(III) terminal and bridged imido [K(18-crown-6)(THF) 2 ]{[(Im Dipp N)Ti(NAd)](μ-NAd) 2 K[Ti(NIm Dipp )]} (10). Altogether, these reactions firmly establish 2 and 3 as unprecedented Ti(I)/Ti(I) and Ti(0)/Ti(0) synthons with the clear capacity to effect multielectron reductions ranging from 4 to 8 electrons.

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Section: Results and Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric “Ti(I)” and “Ti(0)” Synthons Supported by Imidazolin-2-Iminato Ligands

et al. 2022

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“…Rothwell has demonstrated the activity of alkoxide-supported tantalum and niobium , alkoxide complexes in racemic hydrogenations. More recently, Fortier has reported homogeneous titanium complexes that catalyze the hydrogenation of benzene and naphthalene derivatives . Diastereoselective xylene hydrogenation has been described by Marks and co-workers using supported zirconocene complexes, demonstrating that a combination of molecular and heterogeneous catalysis is beneficial for catalyst activity and selectivity. − …”

Section: Introductionmentioning

confidence: 99%

“…More recently, Fortier has reported homogeneous titanium complexes that catalyze the hydrogenation of benzene and naphthalene derivatives. 29 Diastereoselective xylene hydrogenation has been described by Marks and co-workers using supported zirconocene complexes, demonstrating that a combination of molecular and heterogeneous catalysis is beneficial for catalyst activity and selectivity. 30−32 By comparison to their monocyclic counterparts, fused arenes and heteroarenes are less-challenging substrates for hydrogenation.…”

Section: ■ Introductionmentioning

confidence: 99%

Molybdenum-Catalyzed Asymmetric Hydrogenation of Fused Arenes and Heteroarenes

et al. 2022

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The synthesis of enantioenriched molybdenum precatalysts for the asymmetric hydrogenation of substituted quinolines and naphthalenes is described. Three classes of pincer ligands with chiral substituents were evaluated as supporting ligands in the molybdenumcatalyzed hydrogenation reactions, where oxazoline imino(pyridine) chelates were identified as optimal. A series of 2,6-disubstituted quinolines was hydrogenated to enantioenriched decahydroquinolines with high diastereo-and enantioselectivities. For quinoline derivatives, selective hydrogenation of both the carbocycle and heterocycle was observed depending on the ring substitution. Spectroscopic and mechanistic studies established molybdenum η 6 -arene complexes as the catalyst resting state and that partial hydrogenation arises from dissociation of the substrate from the coordination sphere of molybdenum prior to complete reduction. A stereochemical model is proposed based on the relative energies of the respective coordination of the prochiral faces of the arene determined by steric interactions between the substrate and the chiral ligand, rather than through precoordination by a heteroatom.

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“…Such an assignment was performed semi-automatically. For instance, a standard name was automatically tagged as “catalysts” if it contained at least one of the following atoms: Zr [ 21 , 22 ], Rh, Ir, Ru, Pt, Pd, Ni, Fe, Co, Os, Cu [ 23 , 24 ], Re [ 24 ], Ag [ 23 , 25 ], Au [ 23 ], W, Mo [ 26 , 27 ], Ti [ 28 ], Mn [ 29 ], In [ 30 ]. We found that such compounds were often recorded in the Reaxys ® database in the “reagents” field.…”

Section: Computational Proceduresmentioning

confidence: 99%

Prediction of Optimal Conditions of Hydrogenation Reaction Using the Likelihood Ranking Approach

Afonina

Mazitov

Nurmukhametova

et al. 2021

IJMS

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The selection of experimental conditions leading to a reasonable yield is an important and essential element for the automated development of a synthesis plan and the subsequent synthesis of the target compound. The classical QSPR approach, requiring one-to-one correspondence between chemical structure and a target property, can be used for optimal reaction conditions prediction only on a limited scale when only one condition component (e.g., catalyst or solvent) is considered. However, a particular reaction can proceed under several different conditions. In this paper, we describe the Likelihood Ranking Model representing an artificial neural network that outputs a list of different conditions ranked according to their suitability to a given chemical transformation. Benchmarking calculations demonstrated that our model outperformed some popular approaches to the theoretical assessment of reaction conditions, such as k Nearest Neighbors, and a recurrent artificial neural network performance prediction of condition components (reagents, solvents, catalysts, and temperature). The ability of the Likelihood Ranking model trained on a hydrogenation reactions dataset, (~42,000 reactions) from Reaxys® database, to propose conditions that led to the desired product was validated experimentally on a set of three reactions with rich selectivity issues.

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Titanium‐Mediated Catalytic Hydrogenation of Monocyclic and Polycyclic Arenes

Cited by 18 publications

References 30 publications

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric “Ti(I)” and “Ti(0)” Synthons Supported by Imidazolin-2-Iminato Ligands

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric “Ti(I)” and “Ti(0)” Synthons Supported by Imidazolin-2-Iminato Ligands

Molybdenum-Catalyzed Asymmetric Hydrogenation of Fused Arenes and Heteroarenes

Prediction of Optimal Conditions of Hydrogenation Reaction Using the Likelihood Ranking Approach

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