Publication

1-Oxa-2,3-cyclohexadiene (\"2H-isopyran\"): a strained heterocyclic allene undergoing cycloaddition reactions with characteristic typo-, regio- and stereoselectivities

Manfred Schlosser
1991
Journal Articles

Abstract

1-Oxa-2,3-cyclohexadiene (I) can be readily generated by treatment of 5-bromo-3,4-dihydro-2H-pyran with potassium tert-butoxide in the presence of 18-crown-6 and can be trapped with dienes or olefins. Thus, the treatment of I with furan gave 50% yield of Diels-Alder adduct II, whereas with 1,1-diphenylethylene I gave 43% of the [2+2]cycloadduct III. The remarkable regio- and stereoselectivities with which [4+2] and [2+2] adducts are formed suggests a concerted, non-radical cycloaddn. mechanism. [on SciFinder (R)]

Official source

https://infoscience.epfl.ch/entities/publication/7569b754-24b9-42e8-bb47-b8b62218a968

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Manfred Schlosser
1991
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/7569b754-24b9-42e8-bb47-b8b62218a968

About this result

Related concepts (7)

Cycloaddition

In organic chemistry, a cycloaddition is a chemical reaction in which "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity". The resulting reaction is a cyclization reaction. Many but not all cycloadditions are concerted and thus pericyclic. Nonconcerted cycloadditions are not pericyclic. As a class of addition reaction, cycloadditions permit carbon–carbon bond formation without the use of a nucleophile or electrophile.

Theory of forms

The theory of Forms, theory of Ideas, Platonic idealism, or Platonic realism is a metaphysical theory, attributed to the Classical Greek philosopher Plato, suggesting that the physical world is not as real or true as timeless, absolute, unchangeable ideas. Ideas according to this theory, conventionally capitalized and translated as "Ideas" or "Forms", are the non-physical essences of all things, of which objects and matter in the physical world are merely imitations.

Alkyne trimerisation

An alkyne trimerisation is a [2+2+2] cycloaddition reaction in which three alkyne units () react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applicable to organic synthesis. Being a cycloaddition reaction, it has high atom economy. Many variations have been developed, including cyclisation of mixtures of alkynes and alkenes as well as alkynes and nitriles. Trimerisation of acetylene to benzene is highly exergonic, proceeding with a free energy change of 142 kcal/mol at room temperature.