(3—6‐η‐Tricyclo [6.2.2.02,7] dodeca‐3,5,9,11‐tetraene)‐tricarbonyliron, a Stable Transition Metal Complex of “o,p′‐Dibenzene”

Grimme, Wolfram; Schneider, Ernst

doi:10.1002/anie.197707171

Cited by 29 publications

(7 citation statements)

References 15 publications

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“…Nonetheless, despite dogged attempts [8], the stereoselectivity of Fe(CO) 3 -promoted ring opening for geometrically unfettered cyclobutenes has not been determined. The ring-opening reactions of Fe(CO) 4 complexes of strained tricyclic cyclobutenes [9] [10], which presumably lose CO to produce coordinatively unsaturated Fe(CO) 3 -cyclobutene complexes [9] [11], have been studied experimentally (representative examples are shown in the Scheme), but only disrotatory ring opening towards the metal is likely in these systems due to the geometric constraints imposed by the additional fused rings. We have investigated the ring opening of the parent Fe(CO) 3 -cyclobutene model system 2 ) using hybrid HF-DFT calculations to determine whether disrotatory ring opening towards the metal is in fact the preferred mode of ring opening in the absence of geometric constraints.…”

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confidence: 99%

“…NICS Values for stationary points along the pathway for distrotatory ring opening towards the metal 9 ) Schleyer, Sorensen, and co-workers report a value of À 20 at the IGLO/III//B3LYP/6-311 G** level [22b]. 10 ) A comprehensive account of the use of NICS calculations as a measure of antiaromatic character in orbital symmetry-forbidden pericyclic reactions will be reported in due course [24]. The NICS values for the complexed transition structures for conrotatory and disrotatory ring opening away from Fe are more difficult to interpret due to the asymmetry of these species.…”

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confidence: 99%

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Demoniac Intervention in the Thermal Electrocyclic Ring Opening of Cyclobutenes: Fe(CO)3 Complexation of Pericyclic Transition Structures

Tantillo

Hoffmann

2001

HCA

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Dedicated to Professor Edgar Heilbronner on the occasion of his 80th birthday Can metal complexation of organic p-systems alter the stereoselectivity of pericyclic reactions? We address this question for the Fe(CO) 3 -templated electrocyclic ring opening of cyclobutene using hybrid HF-DFT calculations. These calculations show that the preferred pericyclic pathway in the presence of Fe(CO) 3 corresponds to the pathway that is orbital-symmetry-forbidden in its absence, validating predictions made previously based on extended Hückel calculations. The three-dimensional aromaticity of the preferred metalcomplexed transition state is revealed by NICS calculations.

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confidence: 99%

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Demoniac Intervention in the Thermal Electrocyclic Ring Opening of Cyclobutenes: Fe(CO)3 Complexation of Pericyclic Transition Structures

Tantillo

Hoffmann

2001

HCA

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“…In the actual experimental systems in which ring-openings of Fe(CO) 4 -cyclobutenes have been observed (Scheme ), , the situation is slightly different. In these systems, the Fe(CO) 4 -complexed cyclobutene ring is fused to another four-membered ring.…”

Section: The Overall Picturementioning

confidence: 98%

“…Although many reported metal-catalyzed pericyclic reactions have been shown to avoid pericyclic mechanisms, 1 it is thought that the ring-opening reactions of Fe(CO) 4 complexes of strained polycyclic cyclobutenes (representative examples are shown in Scheme 1) 2,3 may in fact involve truly pericyclic reactions. [1][2][3][4] Nonetheless, this matter remains unsettled.…”

Section: Introductionmentioning

confidence: 99%

“…Can the complexation of a metal or organometallic fragment with an organic π-system alter the rate or stereoselectivity of a pericyclic reaction without making it into a stepwise process? Although many reported metal-catalyzed pericyclic reactions have been shown to avoid pericyclic mechanisms, it is thought that the ring-opening reactions of Fe(CO) 4 complexes of strained polycyclic cyclobutenes (representative examples are shown in Scheme ) , may in fact involve truly pericyclic reactions. − Nonetheless, this matter remains unsettled.

1 …”

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confidence: 99%

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Complicated Goings-On in the Metal-Manipulated Ring-Opening of Cyclobutene

Tantillo

Hoffmann

2001

J. Am. Chem. Soc.

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Most reported examples of transition metal-mediated pericyclic reactions have been shown to proceed by nonpericyclic mechanisms. However, the conversion of Fe(CO)(4)-cyclobutenes to Fe(CO)(3)-butadienes and CO is thought to proceed through a mechanism involving an electrocyclic ring-opening step. We have examined this and possible alternative mechanisms for the parent Fe(CO)(4)-cyclobutene complex using hybrid HF-DFT calculations. In this system there is an inherent preference for a pathway that avoids metal-templated electrocyclic ring-opening, but the pericyclic pathway is predicted to dominate for more elaborate substrates and under certain experimental conditions.

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The Retro–Diels–Alder Reaction PartI.CCDienophiles

Rickborn

1998

Organic Reactions

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The Diels–Alder (“DA”) reaction is so familiar to organic chemists that the retro‐Diels–Alder or retro‐diene reaction (hereafter “rDA”) requires no conceptual introduction. However, a working definition is needed to indicate the coverage of this review. The intent is to include all reported examples of the general skeletal process excluded in this chapter. Any of the atoms in the starting material (cycloadduct) may be carbon or heteroatom, and substituents on all positions are allowed. In addition, any bond order available to the element in any oxidation state is included, as well as bonding to non‐nearest neighbor atoms (bicyclics, etc.). The volume of literature required separation of this review into two parts. Part I covers all expelled C–C dienophiles, i.e. those reactions that generate a new carbon‐carbon double or triple bond in the dienophile that is formed. Part II, to appear later, covers those expelled dienophiles in which one or both atoms is a heteroatom. Certain specific topics are intentionally omitted. These are: rDA reactions invoked under mass spectral conditions; rDA reactions of polymeric substrates; Electrocyclic processes, some of which are arguably very similar to rDA reactions (these are not addressed unless needed for clarification of an rDA sequence); and a thorough discussion of homo‐rDA reactions. CAS‐Online searches resulted in ca. 1,300 references, of which ca. 900 proved pertinent to the rDA topic as defined and delimited above. Active literature searching was halted in April 1995, but occasional more recent articles are included. Over 2,500 pertinent references were eventually found. Most were obtained by perusal of primary literature (articles) and secondary sources (books and reviews). Computer based search success was limited mainly by the failure of authors or abstractors to key‐word this topic, an especially common occurrence when the expelled dienophile was a simple substance such as N 2 or CO 2 . Overall, approximately 3,500 books, chapters, reviews, articles, and abstracts were consulted in an effort to make this review as comprehensive as possible. This was done with the certainty that some pertinent literature would be missed, tempered by the view that these omissions are probably also lost to any future rational search method. Many secondary sources proved valuable not only for in‐depth discussion of certain rDA reaction types, but also for providing comparisons with related topics. To assist the reader, these secondary sources are referenced (alphabetically by first author within broad subject areas) with a title or brief note on the topic(s) addressed. The first group lists earlier reviews with primary focus on rDA reactions, followed by items of Historical/General Interest, reviews that deal with Experimental Methods, DA reactions (general and specific), reviews of Related Topics (these impinge in more or less significant ways on rDA reactions), and general treatments of Theory and Mechanism.

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(3—6‐η‐Tricyclo [6.2.2.0^2,7] dodeca‐3,5,9,11‐tetraene)‐tricarbonyliron, a Stable Transition Metal Complex of “o,p′‐Dibenzene”

Abstract: The Diels‐Alder dimer of benzene has now been synthesized in the form of the stable tricarbonyliron complex (1). On liberation by oxidizing cleavage, the dimer immediatedly decomposes to benzene.

Cited by 29 publications

References 15 publications

Demoniac Intervention in the Thermal Electrocyclic Ring Opening of Cyclobutenes: Fe(CO)3 Complexation of Pericyclic Transition Structures

Demoniac Intervention in the Thermal Electrocyclic Ring Opening of Cyclobutenes: Fe(CO)3 Complexation of Pericyclic Transition Structures

Complicated Goings-On in the Metal-Manipulated Ring-Opening of Cyclobutene

The Retro–Diels–Alder Reaction PartI.CCDienophiles

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