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Molecules 2012, 17(2), 1548-1570; doi:10.3390/molecules17021548
Review

Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene

Received: 7 December 2011; in revised form: 13 January 2012 / Accepted: 17 January 2012 / Published: 7 February 2012
(This article belongs to the Special Issue Heterocycles)
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Abstract: Benzo-condensed four-ring heterocycles, such as benzoxetes 1 and benzothietes 3 represent multi-purpose starting compounds for the preparation of various higher heterocyclic ring systems. The thermal or photochemical valence isomerizations between the benzenoid forms 1,3 and the higher reactive o-quinoid structures 2,4 provide the basis for the synthetic applications. On the other hand, this valence isomerization impedes in particular the generation and storage of 1 because the thermal equilibrium 1 2 is completely on the side of 2. Thus, the number of erroneous or questionable benzoxete structures published to date is surprisingly high. On the contrary, the thermal equilibrium 3 4 is on the side of the benzothietes 3, which makes them easily accessible, especially by different flash vacuum pyrolysis techniques. The present article gives a survey of the preparations of 1 and 2, and tries to stimulate their use in synthetic projects. Naphtho-condensed and higher condensed compounds and compounds with an exocyclic C=O or S=O double bond (lactones, thiolactones, sulfoxides and sulfones) are not covered in this article.
Keywords: cycloaddition; flash-vacuum-pyrolysis; photochemistry; ring closure; ring opening cycloaddition; flash-vacuum-pyrolysis; photochemistry; ring closure; ring opening
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Meier, H. Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene. Molecules 2012, 17, 1548-1570.

AMA Style

Meier H. Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene. Molecules. 2012; 17(2):1548-1570.

Chicago/Turabian Style

Meier, Herbert. 2012. "Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene." Molecules 17, no. 2: 1548-1570.



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