Photoequilibriums between 1,3-cyclohexadienes and 1,3,5-hexatrienes. Photochemistry of 3-alkyl-6,6,9,9-tetramethyl-.DELTA.3,5(10)-hexalins

Dauben, William G.; Rabinowitz, J.; Vietmeyer, Noel D.; Wendschuh, P. H.

doi:10.1021/ja00767a042

Cited by 40 publications

(15 citation statements)

References 3 publications

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“…The reverse reaction occurs with a 0.46 quantum yield [83][84][85] in agreement with the predicted relationship Φ CHD→cZc-HT ~ (1-Φ cZc-HT→CHD ). In other substituted and polycyclic molecules 86,87 steric and strain effects may greatly differentiate the slopes of the CHD and cZc-HT valleys leading to values of Φ CHD , Φ cZc-HT far from 0.5.…”

Section: Figure 28mentioning

confidence: 99%

A Computational Strategy for Organic Photochemistry

Robb¹,

Garavelli²,

Olivucci³

et al. 2000

Reviews in Computational Chemistry

205

132

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INTRODUCTION Modeling Photochemical ReactionsThe aim of this chapter is to provide an introduction to the practical computational investigation of photochemical reaction mechanisms. During the last decade or so, the speed of computers has grown considerably, and now the computational investigation of realistic models of organic compounds is becoming a standard practice. Current applications range from the investigation of the mechanism of synthetically useful reactions to the study of shortlived organic intermediates detected in the interstellar medium. For thermal reactions, standard state-of-the-art ab initio quantum chemical methods are already capable of providing a complete description of what happens at the Reviews in Computational Chemistry, Volume 15 87 88 A Computational Strategy for Organic Photochemistry molecular level during bond-breaking and bond-forming processes. In particular, it is possible to compute the transition structure that connects a reactant to a product and the associated energy barrier with almost chemical accuracy (ca. 1 kcal/mol error). Furthermore the reaction path (i.e., the progression of the molecular structure from the reactants toward the transition state and the product) can be determined, in a completely unbiased way, by computing the minimum energy path (MEP)1 connecting the reactant to the product on the (3N -6)-dimensional potential energy surface of the system.A detailed understanding of the reaction pathway in the excited state manifold will increase our ability to design new and to control known photochemical reactions. As an example, the conversion of light into chemical energy in plants and animals involves extended conjugated moleculescarotenoids and retinals-bound in protein complexes. The use of such extended systems in optical data storage and processing technology is now being investigated. Photobiological systems exploit the ability of these chromophores to undergo cis-trans isomerization and to transduce radiative energy into thermal energy on picosecond or shorter time scales. Recent advances in timeresolved spectroscopy2 (e.g., the use of ultrafast laser pulses) have provided a powerful tool to monitor reaction dynamics on the femtosecond time scale and have made direct observation of these processes possible, increasing our understanding of the excited state structures and dynamics for model systems. UItrafast (femtosecond) radiationless decay has been observed, for example, for simple dienes,3 cyclohexadienes,4~5 and hexatrienes,6 and in both free7 and opsin-bound8 retinal protonated Schiff bases. However, a complete understanding of molecular dynamics on multiple electronic states is required to interpret these laser experiments with confidence and to understand the principles involved in the design of optical devices.Until recently, reaction path computations were mainly limited to the investigation of thermal reactions and thus to reactions occurring on a single potential energy surface. Photochemical processes, where the reactant resides on an excited ...

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Section: Figure 28mentioning

confidence: 99%

A Computational Strategy for Organic Photochemistry

Robb¹,

Garavelli²,

Olivucci³

et al. 2000

Reviews in Computational Chemistry

205

132

View full text Add to dashboard Cite

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“…Evidence for the conformer-specificity of the ring-opening in αPH (6) and other reactants (8,9) has been observed in solution-phase measurements of photoproduct ratios. Moreover, resonance Raman Fig.…”

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confidence: 92%

Conformer-specific photochemistry imaged in real space and time

Champenois

Sanchez

Yang

et al. 2021

Science

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Conformer-specific dynamics Conformation-dependent dynamics play an important role in organic chemistry syntheses such as electrocyclic reactions, as well as in biological processes such as protein folding. However, current time-resolved experimental methods struggle to distinguish conformers from each other, and conformational isomerism is usually analyzed through reactant and product distributions. Using a combination of mega–electron volt ultrafast electron diffraction and quantum wave packet simulations, Champenois et al . directly followed the photochemical electrocyclic ring opening of the molecule α-phellandrene with femtosecond time resolution and confirmed that the transformation of a specific molecular conformer follows the famous Woodward-Hoffmann rules. The proposed method is potentially a powerful tool to follow conformer specificity in various organic and biological systems in real time. —YS

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“…A reasonable mechanistic pathway is base-catalyzed alkene isomerization to conjugated hexatriene derivative 5a followed by disrotatory 6 electrocyclic ring closure, 4 which establishes the relative stereochemistry at the junction of the oxanorbornene and cyclohexadiene rings. The stereochemistry of the other ester group was assigned based on the 4 Hz coupling constant between the bridgehead H and the H alpha to the ester group, which is consistent with only the indicated isomer.…”

Section: Resultsmentioning

confidence: 99%

A novel stereoselective [8+2] double cycloaddition route to hydronaphthalene ring systems

Ying

Zhang

Wiget

et al. 2016

Tetrahedron Letters

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Substituted hydronaphthalenes where each of the ten carbons of the two-ring system contains functionality were obtained through a tandem [8+2] cycloaddition and base-catalyzed rearrangement process using dienylfurans and electron-deficient alkynes. If the [8+2] process is conducted under solvent-free conditions the process could be conducted in a single reaction flask without isolation of the chromatographically sensitive [8+2] cycloadducts. A mechanism involving base catalysed alkene positional isomerization followed by disrotatory electrocyclic ring closure was proposed for the key reaction step that converts [8+2] cycloadducts to hydronaphthalenes. The products undergo selective ring opening-isomerization processes upon treatment with Lewis acids.

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Photoequilibriums between 1,3-cyclohexadienes and 1,3,5-hexatrienes. Photochemistry of 3-alkyl-6,6,9,9-tetramethyl-.DELTA.3,5(10)-hexalins

Cited by 40 publications

References 3 publications

A Computational Strategy for Organic Photochemistry

A Computational Strategy for Organic Photochemistry

Conformer-specific photochemistry imaged in real space and time

A novel stereoselective [8+2] double cycloaddition route to hydronaphthalene ring systems

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