Valenzisomerisierungen von Cyclobutenen

Criegee, Rudolf; Seebàch, Dieter; Winter, Rudolph Ernst K.; Børretzen, B; Brune, Hans Albert

doi:10.1002/cber.19650980738

Cited by 98 publications

(37 citation statements)

References 40 publications

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“…For example, the ring opening of cisbicyclo[4.2.0]oct-7-ene (80) to cis,cis-cycloocta-1,3-diene (81) was first reported in 1965. 46 Baldwin et al examined a deuterium kinetic isotope effect using deuterated bicyclo[4.2.0]oct-7-ene. 47 The results were inconsistent with a mechanistic scenario involving cis,trans-cycloocta-1,3-diene (82), which led the authors to conclude that a direct disrotatory ring opening route was the preferred mechanism (Scheme 39).…”

Section: Phmentioning

confidence: 99%

5.16 Cyclobutene Ring Opening Reactions

Murakami¹,

Matsuda²

2014

Comprehensive Organic Synthesis II

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Section: Phmentioning

confidence: 99%

5.16 Cyclobutene Ring Opening Reactions

Murakami¹,

Matsuda²

2014

Comprehensive Organic Synthesis II

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“…Several Criegee papers on this topic were published in 1965 and later. [58,[65][66][67][68][69] In 1964, Criegee was still absorbed in and focused on alternate methods to synthesize substituted cyclobutenes including [2 + 2]photocyclizations. [70] * Waldemar Adam was a postdoctoral student in Criegee's laboratory in 1962.…”

Section: Assembling the Experiencesmentioning

confidence: 99%

The Many Chemists Who Could Have Proposed the Woodward‐Hoffmann Rules But Didn't: The Organic Chemists Who Discovered the Smoking Guns^[^]**

Seeman

2022

The Chemical Record

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It is a reasonable question to ask, why, as of 1965 when the five Woodward‐Hoffmann communications appeared, did no other organic chemist discover the orbital symmetry rules for pericyclic reactions? Two theoretical chemists – Luitzen Oosterhoff (in 1961) and Kenichi Fukui (in 1964) had discovered portions of the orbital symmetry rules before Woodward and Hoffmann. Why not organic chemists? Indeed, perhaps the greatest motivation to discover the mechanism of a mysterious reaction is to uncover key examples of that mysterious reaction in your very own laboratory. The stories of 20 chemists and R. B. Woodward are discussed in this paper which is Paper 6 in a 27‐paper series on the history of Woodward‐Hoffmann rules. Social, political, and scientific explanations will also be presented as partial explanations as to why none of these individuals – except Woodward with Hoffmann – solved the pericyclic no‐mechanism problem.

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“…In this study, Walters and coworkers concluded that the process is unimolecular, and it occurs at 150°C. At the same time Vogel and Criegee and coworkers reported stereochemical studies of the ring‐opening of the 3,4‐disubstituted cyclobutenes leading to a considerable understanding of the mechanism.…”

Section: The Topography Of the Cyclobutene Isomerization To Butadienementioning

confidence: 99%

Embedding of the saddle point of index two on the PES of the ring opening of cyclobutene

Quapp

Bofill

2015

Int. J. Quantum Chem.

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The ring opening of cyclobutene is characterized by a competition of the two different pathways: a usual pathway over a saddle of index one (SP 1 ) along the conrotatory behavior of the end groups, as well as a "forbidden" pathway over a saddle point of index two (SP 2 ) along the disrotatory behavior of the end CH 2 groups. We use the system of ordinary differential equations for the method of the gentlest ascent dynamics (GAD) to determine saddle points of the potential energy surface (PES) of the ring opening of cyclobutene to cis-butadiene. We apply generalized GAD formulas for the search of a saddle point of index two. To understand the relation of the different regions of the PES (around minimums, around SPs of index one or two) we also calculate valley-ridge inflection (VRI) points on the PES using Newton trajectories (NT). VRIs and the corresponding singular NTs subdivide the regions of "attraction" of the different SPs. We calculate the connections of the SP 2 (in its different symmetry versions) with different SPs of index one of the PES by different "reaction pathways." We compare the possibilities of the tool of the GAD curves for the exploration of PESs with these of NT. The barrier of the disrotatory SP 2 is somewhat higher than the barrier of the conrotatory SP 1 , however, pathways across the slope to the SP 2 open additional reaction valleys. IntroductionMathematics has had a profound impact on science, providing a means to understand the world around us in unprecedented ways.[1] With the advantage of the computer age, the subject of modelization has hugely grown in importance. In particular, over the last decades significant advances in our understanding of the world of chemistry have culminated in the development of a very large set of concepts. Some of these concepts are the potential energy surface (PES) [2][3][4] and the chemical reaction path (RP) [5] being the basic concepts for the theories of chemical dynamics and chemical transformations. The PES is a continuous function of the coordinates of the nuclei over an IR N , thus it is an N-dimensional hypersurface. It should have continuous derivatives of at least second order for our treatments. If Cartesian coordinates are used, then N53 n, however, we may also use N53 n26 nonredundant, internal coordinates for an n-atomic molecule. The PES can be seen as formally divided in catchments associated with local minima.[2] For such a picture, one has in mind steepest descent (SD) curves. The first order saddle points or transition states (TSs) are located at the deepest points of the boundary of the basins. TSs and minima correspond to stationary points of the PES. Two adjacent minima of the PES can be connected through a TS via a continuous curve in the N-dimensional coordinate space, describing the coordinates of the nuclei. The curve characterizes a RP. The concept of the RP has found a widespread use in descriptions of reaction mechanisms, which are based on geometrical rearrangements of the atoms comprising a given chemical system. [6] Mor...

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Valenzisomerisierungen von Cyclobutenen

Cited by 98 publications

References 40 publications

5.16 Cyclobutene Ring Opening Reactions

5.16 Cyclobutene Ring Opening Reactions

The Many Chemists Who Could Have Proposed the Woodward‐Hoffmann Rules But Didn't: The Organic Chemists Who Discovered the Smoking Guns^[^]**

Embedding of the saddle point of index two on the PES of the ring opening of cyclobutene

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Valenzisomerisierungen von Cyclobutenen

Cited by 98 publications

References 40 publications

5.16 Cyclobutene Ring Opening Reactions

5.16 Cyclobutene Ring Opening Reactions

The Many Chemists Who Could Have Proposed the Woodward‐Hoffmann Rules But Didn't: The Organic Chemists Who Discovered the Smoking Guns[]**

Embedding of the saddle point of index two on the PES of the ring opening of cyclobutene

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The Many Chemists Who Could Have Proposed the Woodward‐Hoffmann Rules But Didn't: The Organic Chemists Who Discovered the Smoking Guns^[^]**