A Promising New Dearomatization Agent:  Crystal Structure, Synthesis, and Exchange Reactions of the Versatile Complex TpRe(CO)(1-methylimidazole)(η2-benzene) (Tp = Hydridotris(pyrazolyl)borate)

Meiere, Scott H.; Brooks, Benjamin C.; Gunnoe, T. Brent; Sabat, and Michal; Harman, W. Dean

doi:10.1021/om000900o

Cited by 55 publications

(86 citation statements)

References 22 publications

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“…Providing support for this notion is the nitrosyl stretching frequency that shifts from 1554 cm -1 for typical dihydropyridine complexes to 1608, 1585, or 1608 cm -1 , for 2, 3, or 4 respectively. 3 Meanwhile, the W(I/0) reduction potential for 2-4 is nearly 0.5 V more positive than that of dihydropyridine complexes.…”

Section: Resultsmentioning

confidence: 94%

“…3 With tungsten coordinating C3 and C4, the acetylated pyridine ring of 1 readily undergoes regio-and stereoselective nucleophilic addition at C2, providing a facile route to a broad range of  2 -(1,2-dihydropyridine) complexes. Presumably, the formation of the cyanine complex 2 is driven in part by the π-basic nature of the metal fragment.…”

Section: Resultsmentioning

confidence: 99%

“…Given the prominent role of π-allyl intermediates in  2 -aromatic chemistry, 3,4 and their potential as synthons for  2 -dienes (vide supra), we sought to understand better the structural features of the TpW(NO)(PMe 3 )(π-allyl) complexes. X-ray data were obtained from single crystals of allyl complexes 3 and 5.…”

Section: Structural Analysis Of Tpw(no)(pme 3 )(π-Allyl) Complexesmentioning

confidence: 99%

“…In this manner,  2 -arene,  2 -pyrrole, and  2 -furan complexes have been utilized in novel organic syntheses. [1][2][3] However, the development of parallel chemistry for pyridines, diazines, diazoles, and other basic aromatic heterocycles has been hampered by the thermodynamic preference of the transition metal to coordinate at nitrogen (Scheme 1, Path A). While such coordination for pyridines can be avoided by strategic placement of substituents (e.g., 2,6-disubstituted pyridines), 4 we desired a more general method for the preparation of dihapto-coordinated complexes of basic heterocycles.…”

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confidence: 99%

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Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe3)}

Harrison¹

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Chapter 1 introduces the traditional organic chemistry of pyridine with an emphasis on its dearomatization. Organometallic methods of dearomatization are also discussed. Strategies for averting nitrogen coordination (i.e. κN) in favor of haptotropic (i.e. η 2 , η 4 , η 6 ) pyridine coordination are discussed, as well as known modifications of these carbon-coordinated pyridines. The work previously performed by our group with {TpW(NO)(PMe 3 )} and our strategy to utilize this fragment is introduced.Chapters 2 and 3 report our findings on the large scale synthesis of η 2 -pyridine complexes of tungsten, utilizing a borane-protection strategy to avert κN coordination.The reactivity of complexes that result from the removal of the borane and replacement with alternative electrophilic groups are investigated. In particular, we have found that an acetyl group provides an isolable N-acetylpyridinium complex, which allows for the mild regio-and stereoselective modification of the pyridine ring with nucleophiles.Chapters 4 and 5 report on the fundamentally new chemistry of pyridine that results from the coordination of the {TpW(NO)(PMe 3 )}. Tandem electrophilic followed by nucleophilic additions and cycloadditions with 1,2-dihydropyridine (DHP) complexes are reported. These findings suggest that the metal coordination reverses the polarization of the pyridine ring carbons such that electrophiles add α-to-N rather than β-to-N. Importantly, we report the isolation of new 2-, 3-, or 4-substitituted piperidine compounds that result from this methodology.Chapter 6 reports pyridine ring scission with nucleophiles capable of delivering 4 e -(2σ, 2π) to the pyridine ring. The resulting conjugated complexes were probed for iii fluorescent activity. While none was found for the metal complexes, photolysis liberated an organic cation that did display fluorescence.Chapter 7 discusses our discovery of highly distorted allyl complexes of {TpW(NO)(PMe 3 )}. Here we endeavor to understand the origin of the large distortions and orientations of allyls observed in crystal structures and reproduced by density functional theory (DFT) calculations. We propose that the nitrosyl is responsible for the distortion, while Tp is responsible for the orientation of the allyls distal to PMe 3 .iv

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Structural Analysis Of Tpw(no)(pme 3 )(π-Allyl) Complexesmentioning

confidence: 99%

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Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe3)}

Harrison¹

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“…The syntheses of complexes incorporating thiazole, pyrazole, imidazole, and amine based ancillary ligands provided access to more electron-rich rhenium complexes (11-17, Table 2). The increased electron density with the incorporation of strong σ-donor ancillary ligands is also demonstrated by comparing νCO of entries 1-10 with 11-17 in Table 2 65 Despite the limited coordination scope of {TpRe(L)(CO)} fragments compared to {Os(NH3)5} 2+ and {TpRe(MeIm)(CO)}, the ability to modulate the chemical environment within a given aromatic ligand (e.g., naphthalene, furan) with changes to L ({TpRe(L)(CO}) allows possible access to range of reactivity for each aromatic ligand.…”

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confidence: 78%

Development of 2nd Row Molybdenum Dearomatization Agents

Shivokevich¹

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ii I am fortunate to have so many people to thank. I truly would not be here, having written all of the pages before you if it weren't for the huge amounts of love and support that I have received from so many along the way. Most of the people listed in this section know that I have a difficult time expressing my feelings. I will attempt to overcome that difficulty here and hopefully give a small amount of something back to all those who have contributed so much to me. I know that I will not do justice to the feelings that I have, but will try my best to express them here. With that in mind, know that as you read on that this was the most difficult, and time consuming part of my thesis to write. It is because I have been fortunate enough to come into contact with a great many wonderful people that any of the subsequent chapters exist; so to say that these acknowledgements are the foundation of my thesis would be an understatement.So here we go. I will start with those who have supported me from the start, my parents. My parents have always encouraged, nurtured, loved and supported me in any venture that I have undertaken. As teachers, they have shown me the importance of education in so many ways. As their way of life, in their professional lives, and also at home. They always stressed the importance of reading, but also looked to establish education in other less traditional ways. These have included travel, and along the way sparked my love of both history and the outdoors, which have continued to be passions of mine to this day. Through my parents I also learned a great deal about the world around me that was not covered in the classroom curriculum. Learning how to build and fix things from my Dad has been a skill that has helped me countless times throughout life, although it also came with the unfortunate side effect of having to constantly fix the rotovap. My Dad also instilled in me the time and money sinks of boating and woodworking, both of which have given me countless hours of joy, and a means of finding peace at stressful times in my life as an adult. In the classroom my parents taught me to iii appreciate all subjects, which I did (except for English class, I hate grammar as anyone at Dean's writing workshop could tell you). This eventually led me to chemistry, which astonished my parents. I went off to college and pursued chemistry, becoming more interested as classes progressed, although I still could not shake my humanities leaning, and ended up with degrees in both chemistry and history.My parents continued to give me support when I set off for Charlottesville. They helped in my apartment search and moving the large amount of stuff that I had accumulated. They then made several house hunting trips, and we drove circles around Charlottesville and the surrounding counties. When I finally bought my first home in the spring of my first year, they both used nearly all of their vacation time to come down and help me with the seemingly endless remodels. I never could have finished it without them. All ...

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TpRe(L)(Br)₂(Tp = hydridotris(pyrazolyl)borate); L = ^tBuNC, PMe₃, pyridine (py), 1-methylimidazole (MeIm))

Meiere

Harman

2002

Encyclopedia of Reagents for Organic Synthesis

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A Promising New Dearomatization Agent: Crystal Structure, Synthesis, and Exchange Reactions of the Versatile Complex TpRe(CO)(1-methylimidazole)(η²-benzene) (Tp = Hydridotris(pyrazolyl)borate)

Cited by 55 publications

References 22 publications

Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe<sub>3</sub>)}

Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe<sub>3</sub>)}

Development of 2nd Row Molybdenum Dearomatization Agents

TpRe(L)(Br)₂(Tp = hydridotris(pyrazolyl)borate); L = ^tBuNC, PMe₃, pyridine (py), 1-methylimidazole (MeIm))

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A Promising New Dearomatization Agent: Crystal Structure, Synthesis, and Exchange Reactions of the Versatile Complex TpRe(CO)(1-methylimidazole)(η2-benzene) (Tp = Hydridotris(pyrazolyl)borate)

Cited by 55 publications

References 22 publications

Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe<sub>3</sub>)}

Highly Functionalized Piperidine Generation via Pyridine Repolarization and Hyper-Distorted Allyl Complexes of {TpW(NO)(PMe<sub>3</sub>)}

Development of 2nd Row Molybdenum Dearomatization Agents

TpRe(L)(Br)2(Tp = hydridotris(pyrazolyl)borate); L = tBuNC, PMe3, pyridine (py), 1-methylimidazole (MeIm))

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A Promising New Dearomatization Agent: Crystal Structure, Synthesis, and Exchange Reactions of the Versatile Complex TpRe(CO)(1-methylimidazole)(η²-benzene) (Tp = Hydridotris(pyrazolyl)borate)

TpRe(L)(Br)₂(Tp = hydridotris(pyrazolyl)borate); L = ^tBuNC, PMe₃, pyridine (py), 1-methylimidazole (MeIm))