A Surprising Switch from the Myers–Saito Cyclization to a Novel Biradical Cyclization in Enyne–Allenes: Formal Diels–Alder and Ene Reactions with High Synthetic Potential

Schmittel, Michael; Keller, Manfred; Kiau, Susanne; Strittmatter, Marc

doi:10.1002/chem.19970030521

Cited by 101 publications

(60 citation statements)

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“…All solvents were distilled prior to use for column chromatography. 3,3,4,4,5,5,6,6,6‐Nonafluorohex‐1‐yne,34 2‐(2‐phenylethynyl)benzaldehyde,24 2‐[2‐( p ‐tolyl)ethynyl]benzaldehyde,1b 2‐(3,3‐dimethylbut‐1‐ynyl)benzaldehyde,35 and 1‐[2‐(2‐phenylethynyl)phenyl]pentan‐1‐ol8b were synthesized according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

et al. 2014

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A series of fluoroalkyl‐substituted enyne‐allenes have been synthesized by a new route with the aim of elucidating the possibility of a fluoro‐ene reaction via an intermediate fulvenyl diradical generated in the thermal C2–C6 (Schmittel) cyclization reaction. As a result of the strong C–F bond, fluorine atom transfer was not observed. Instead, 1H‐cyclobuta[a]indenes were formed in good yields despite the high strain energy. DFT calculations at the B3LYP level of theory indicated that although the fluoro‐ene reaction is the most exothermic reaction available, cyclobutene formation is kinetically favored over the [1,5]‐fluorine shift by 5–15 kcal mol–1 in various model compounds.

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Section: Methodsmentioning

confidence: 99%

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

et al. 2014

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“…79,80 These compounds rearrange to give a product that can be formally considered to have undergone first a Schmittel cyclization to give the diradical 55, which then transfers a hydrogen atom to give the product 56. In this section, we take on the Schmittel-type cyclization of the C 1 -alkyl-substituted enyne-allenes 54.…”

Section: -C 6 Enyne Allene Cyclizationmentioning

confidence: 99%

Organic Reaction Dynamics

Bachrach

2014

Computational Organic Chemistry

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In the previous chapters, we have focused our discussion of reaction mechanisms on the critical points along the reaction path. These critical points-local energy minima (reactants, intermediates, and products) and transition states (TSs)-were discussed in terms of their geometries and energies. We discussed the nature of the mechanism in terms of the topology of the potential energy surface (PES), the structure of the TSs, and the presence or absence of intermediates. We think of reactants progressing over TSs on to intermediates, perhaps through multiple intermediates and ending at products. This path is called the reaction coordinate and corresponds to the intrinsic reaction coordinate (IRC) or the minimum energy path (MEP) (see Section 1.6 for discussion on these two paths).This standard mechanistic analysis has a long successful history. Organic chemistry textbooks are filled with PESs and discussions of the implication of single-step versus multiple-step mechanisms, concerted TSs, and so on. 1,2 Transition state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory provide tools for predicting rates based upon simple assumptions built upon the notion of reaction on the PES following the reaction coordinate. 3,4 An often-overlooked aspect of standard reaction mechanistic thought is that it really addresses only half of the picture. We talk about the positions of the atoms during the course of the reaction and the relative energies of points along the reaction path, but no mention is made of the time evolution of this process. In classical mechanics, description of a reactive system requires not just the particle positions but their momenta as well. The same is true for a quantum mechanical description, though one must keep in mind the limits imposed by the Heisenberg Uncertainty Principle. A complete description of a molecular reaction requires knowledge of both the position and the momentum of every atom for the entire time it takes for reactants to convert into products. This kind of description falls under the term molecular dynamics (MD).A few simple examples should suffice to demonstrate the critical role that MD plays in chemical reactions. Conservation of momentum must be enforced. Atoms and molecular fragments in motion must maintain their motion unless some barrier or force is applied to them. Consider the reaction of cis-2-butene with Computational Organic Chemistry, Second Edition. Steven M. Bachrach

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“…Diethyl ether and tetrahydrofuran (THF) were distilled from benzophenone ketyl prior to use. 3,187.7,150.0,147.5,145.1,142.6,142.2,142.0,141.6,140.1,139.7,137.9,135.7,135.4,134.88,134.79,134.36,134.28,133.9,133.3,131.33,131.24,131.20,130.22,130.11,129.63,129.59,129.3,129.15,129.11,128.8,128.56,128.37,128.15,127.91,127.83,124.5,123.5,123.02,122.96,122.8,120.0,57.6;13 C (CDCl 3 ,150 MHz) δ 190.6,188.1,149.7,146.9,145.3,142.0,141.8,141.6,140.8,139.5,139.1,138.1,135.2,…”

Section: General Experimental Methodsmentioning

confidence: 99%

“…The current research on the thermal biradical cyclization of enyne−allenes is not only focused on the synthesis of simple model compounds with potential antitumor and antibiotic activities mimicing the naturally occurring enediyne antitumor antibiotics, but also on using them for the construction of polycyclic ring systems. 3 In particular, the Schmittel cyclization reaction has played an important role in the synthesis of carbocyclic 4 and heterocyclic 5,6 ring systems, beacuse the biradical intermediate may undergo a rapid radical−radical coupling reaction leading to the formal Diels−Alder adducts that provide easy access to polycyclic aromatic systems.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of polycyclic aromatics having unusual molecular architectures via cascade cyclization reactions of enyne -allenes

Wang¹

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Synthesis of Polycyclic Aromatics Having Unusual Molecular Architectures via Cascade Cyclization Reactions of Enyne-Allenes YU-HSUAN WANG The C 2 −C 6 Schmittel cyclization reaction of the benzannulated enyne−allenes provides an efficient synthetic pathway for the construction of a variety of polycyclic aromatics. By starting from truxenone, the cascade cyclization reactions furnished several unusual and congested polycyclic compounds. The in situ generated enyne−allenes are key intermediates in these cyclization reactions. A new synthetic approach to 2,2′-disubstituted 1,1′-binaphthyls and related compounds was also successfully developed by using the benzannulated enediynes as precursors. These 1,1′-binaphthyls derivatives can serve as potential BINOL type ligands. The assembly of the enediynyl precursors from three separate aromatic fragments allows the possibility of placing a variety of functional groups at various positions of the 1,1′-binaphthyl system. A 12-step non-pyrolytic synthetic pathway employing the Schmittel cyclization reactions has been developed, leading to a bowl-shaped polycyclic aromatic hydrocarbon (PAH) having a 54-carbon framework of the surface of C 60. Incorporating of sp 3-carbons on the 54-carbon framework facilitates the connection of carbon atoms intramolecularly. iii Dedicated to My parents, brother, Leo, and sisters iv ACKNOWLEDGMENTS Firstly, I would like to express sincere appreciation to my advisor, Dr. Kung K. Wang, for his continuous support and encouragement during the past five years. His great patience and knowledge in chemistry guided me to solve so many problems. I was so pleased and lucky to have associated with this outstanding teacher and chemist. The way of his teaching not only benefits me academically but also led me to have a logical thinking when seeing through a problem. His enthusiasm and optimism are always my driving force to keep forward. My special thanks go to Dr. Jeffery Petersen for his significant work in X-ray crystal structure analysis. His work really helped me in identification of product structure which made my research keep forward. Also, Dr. Novruz.Akhmedov is greatly appreciated for his assistance in NMR studies of lots of my products. In addition, I would like to thank the rest of my research committee members, Dr. George A. O'Doherty, Dr. Peter M. Gannett, and Dr. John Penn for their valuable suggestions and discussion on my dissertation. My appreciation is also extended to the former and present group members, Dr. Hua Yang, Dr.

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A Surprising Switch from the Myers–Saito Cyclization to a Novel Biradical Cyclization in Enyne–Allenes: Formal Diels–Alder and Ene Reactions with High Synthetic Potential

Cited by 101 publications

References 62 publications

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

Organic Reaction Dynamics

Synthesis of polycyclic aromatics having unusual molecular architectures via cascade cyclization reactions of enyne -allenes

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A Surprising Switch from the Myers–Saito Cyclization to a Novel Biradical Cyclization in Enyne–Allenes: Formal Diels–Alder and Ene Reactions with High Synthetic Potential

Cited by 101 publications

References 62 publications

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C2–C6 Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C2–C6 Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

Organic Reaction Dynamics

Synthesis of polycyclic aromatics having unusual molecular architectures via cascade cyclization reactions of enyne -allenes

Contact Info

Product

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Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation

Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C²–C⁶ Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation