The preparation and isomerization of - and -3,4-dimethylcyclobutene.

Winter, Rudolph Ernst K.

doi:10.1016/s0040-4039(01)83997-6

Cited by 40 publications

(22 citation statements)

References 9 publications

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“…15 and eq. 16) [68] . These two cyclobutenes are the least substituted hydrocarbon analogues of Vogel's 1954 seminal result (eq.…”

Section: The First Chemical Hints Of a Major Chemical Problemmentioning

confidence: 89%

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History of the Woodward‐Hoffmann Rules. The No‐Mechanism Puzzle**

Seeman

2022

The Chemical Record

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This is Paper 2 in the 27‐paper series on the history of the development of the Woodward‐Hoffmann rules. Paper 2 takes the reader back to the 1950s and early 1960s, before the publication of the first Woodward‐Hoffmann paper in January 1965. The scope of the pericyclic no‐mechanism problem is described along with many of the key “hints” or “clues” to orbital symmetry control that were available in the literature prior to 1965. A chronology of reactions with alternating stereospecificities is provided. A second chronology of alternating theoretical hints is provided, e. g., 4n+2 versus 4n. Another chronology is provided, that of the development of frontier molecular orbital theory, with and without phases and nodes. A tabulation is provided of 36 instances in which the MOs of 1,3‐butadiene were reported in the literature. A knowledge of the MOs of 1,3‐butadiene, plus a knowledge of some of the alternating stereospecific reactions, could have led many chemists to the solution of the pericyclic no‐mechanism problem before Woodward and Hoffmann.

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“…15 and eq. 16) [68] . These two cyclobutenes are the least substituted hydrocarbon analogues of Vogel's 1954 seminal result (eq.…”

Section: The First Chemical Hints Of a Major Chemical Problemmentioning

confidence: 89%

“…4). Winter performed these experiments in the summer of 1963 as a postdoctoral fellow in Criegee's laboratory in Karlsruhe, two years before Woodward‐Hoffmann [68] …”

Section: The First Chemical Hints Of a Major Chemical Problemmentioning

confidence: 99%

History of the Woodward‐Hoffmann Rules. The No‐Mechanism Puzzle**

Seeman

2022

The Chemical Record

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“…In the case of trans ‐3,4‐disubstituted cyclobutenes, the disadvantage of the inward transition state in which both substituents rotate in the sterically unfavorable direction would be enormous. For example, (2 E ,4 E )‐hexadiene ( 2 ) is exclusively formed during the ring‐opening of trans ‐3,4‐dimethylcyclobutene ( 1 ) (Scheme ) 10. The calculated energy difference of the inward and outward transition states amounts to 13.0 kcal mol −1 (RHF/3‐21G) 4b.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Thermal Ring Opening of trans‐3,4‐Disilylcyclobutene

Murakami

Hasegawa

2004

Angew Chem Int Ed

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In the reaction described by M. Murakami and M. Hasegawa on the following pages, the electronic effects are so dramatic that the sterically hindered substrate prefers to react by a more crowded pathway. This reaction will provide organic chemistry textbooks with a prime example of systems in which electronic effects are dominant over steric effects in determining the stereochemical outcome of a reaction. 4873

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“…Trans-3,4-disubstituted cyclobutenes are known to undergo one of the conrotatory isomerizations shown below depending on the identities of R and RЈ, [19][20][21] Letting R and RЈ be methyl groups, we initiated a series of searches from the configuration shown in Fig. 6.…”

Section: B Trans-14-dimethylcyclobutene Rearrangementmentioning

confidence: 99%

“…Experiments have shown that trans, trans hexadiene is the only product formed upon heating trans-dimethylcyclobutene. 19,20 Thus, if any additional pathways for the conversion of trans-1,4-dimethylcyclobutene exist, they should possess higher activation barriers than the barrier for pathway 1.…”

Section: ͑15͒mentioning

confidence: 99%

Biasing a transition state search to locate multiple reaction pathways

Peters

Liang

Bell

et al. 2003

The Journal of Chemical Physics

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Articles you may be interested inAb initio reaction pathways for photodissociation and isomerization of nitromethane on four singlet potential energy surfaces with three roaming paths Development and application of a hybrid method involving interpolation and ab initio calculations for the determination of transition states A variety of chemical systems exhibit multiple reaction pathways that adjoin to a common reactant state. In fact, any reaction producing side products or proceeding via a stable intermediate involves a species possessing at least two reaction pathways. Despite improvements in ab initio transition-state search algorithms it remains difficult to detect multiple reaction pathways. Typically, multiple reaction pathways can only be detected by intuitively varying the initial point in the transition-state search trajectory. This reliance on intuition limits the ability to discover new and unexpected chemistry using ab initio methods. This paper proposes a systematic and intuition-free method for biasing a transition-state search to identify multiple reaction pathways originating from a common reactant state. The method allows the successive location of transition states, with each successful search contributing to a cumulative bias potential for the following search. The method is applicable to all psuedo-Newton-Raphson-type transition-state searches. The procedure was tested for a model potential energy surface and for the thermal rearrangement of trans-1,4-dimethylcyclobutene. In the latter case, four reaction pathways were discovered: two exothermic conrotatory ring openings leading to hexadienes, an endothermic methyl migration pathway leading to a carbene, and an exothermic rearrangement leading to 3-methyl-1,4-pentadiene. In accordance with experiment, the calculations predict that the conrotatory pathway leading to trans,trans-2,4-hexadiene is the kinetically dominant pathway. The methodology was also used to compute selectivities for competitive pathways producing trans and cis triflouropentadiene products in the thermal rearrangement of 3-triflouromethyl-cyclobutene. Again, results were in accord with experimental observations.

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The preparation and isomerization of - and -3,4-dimethylcyclobutene.

Cited by 40 publications

References 9 publications

History of the Woodward‐Hoffmann Rules. The No‐Mechanism Puzzle**

History of the Woodward‐Hoffmann Rules. The No‐Mechanism Puzzle**

Synthesis and Thermal Ring Opening of trans‐3,4‐Disilylcyclobutene

Biasing a transition state search to locate multiple reaction pathways

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