Posts Tagged ‘electrocyclic’

Woodward’s symmetry considerations applied to electrocyclic reactions.

Monday, May 20th, 2013
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Sometimes the originators of seminal theories in chemistry write a personal and anecdotal account of their work. Niels Bohr[1] was one such and four decades later Robert Woodward wrote “The conservation of orbital symmetry” (Chem. Soc. Special Publications (Aromaticity), 1967, 21, 217-249; it is not online and so no doi can be given). Much interesting chemistry is described there, but (like Bohr in his article), Woodward lists no citations at the end, merely giving attributions by name. Thus the following chemistry (p 236 of this article) is attributed to a Professor Fonken, and goes as follows (excluding the structure in red):

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References

  1. N. Bohr, "Der Bau der Atome und die physikalischen und chemischen Eigenschaften der Elemente", Zeitschrift f�r Physik, vol. 9, pp. 1-67, 1922. http://dx.doi.org/10.1007/BF01326955

So near and yet so far. The story of the electrocyclic ring opening of a cyclohexadiene.

Tuesday, December 6th, 2011
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My previous three posts set out my take on three principle categories of pericyclic reaction. Here I tell a prequel to the understanding of these reactions. In 1965, Woodward and Hoffmann published their theoretical analysis (submitted Nov 30, 1964) for which the Nobel prize (to Hoffmann only of the pair, Woodward having died) was later awarded. But in the same year, Elias Corey reported the conclusion of a project started several years earlier (first reported Nov 1, 1963) to synthesize the sesquiterpene dihydrocostunolide.

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A modern take on the pericyclic electrocyclic ring opening of cyclobutene.

Saturday, November 26th, 2011
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Woodward and Hoffmann published their milestone article  “Stereochemistry of Electrocyclic Reactions” in 1965. This brought maturity to the electronic theory of organic chemistry, arguably started by the proto-theory of Armstrong some 75 years earlier. Here, I take a modern look at the archetypal carrier of this insight, the ring opening of dimethylcyclobutene.

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