Synthesis of o-quinodimethanes and benzocyclobutenes from dimethyl squarate

Selected 3-alkylidene(and benzylidene)-4-allenylcyclobutenes were shown to undergo an unusual thermal ring expansion to o-quinodimethanes and thus to benzocyclobutenes upon electrocyclic ring closure. The mechanism of this rearrangement is envisaged to involve ring opening of the starting cyclobuten...

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Bibliographic Details
Published inTetrahedron letters Vol. 34; no. 39; pp. 6177 - 6180
Main Authors Ezcurra, John E., Moore, Harold W.
Format Journal Article
LanguageEnglish
Published OXFORD Elsevier Ltd 24.09.1993
Elsevier
Subjects
Alicyclic compounds
Alicyclic compounds, terpenoids, prostaglandins, steroids
Chemistry
Chemistry, Organic
Exact sciences and technology
Organic chemistry
Physical Sciences
Preparations and properties
Science & Technology
Wittig reaction
Pyrolysis
Electrocyclic reaction
Ether
Bicyclic compound
Reaction mechanism
Phenols
Aromatic compound
Enol ether
Allenic compound
Monocyclic compound
Ring expansion
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Summary:Selected 3-alkylidene(and benzylidene)-4-allenylcyclobutenes were shown to undergo an unusual thermal ring expansion to o-quinodimethanes and thus to benzocyclobutenes upon electrocyclic ring closure. The mechanism of this rearrangement is envisaged to involve ring opening of the starting cyclobutenes to the corresponding octa-1,2,4,6,7-pentaenes which lead to the quinodimethanes upon ring closure. 3-Alkylidene(or benzylidene)4-allenylcyclobutenes lead to quinodimethanes and thus benzocyclobutenes upon thermolysis. The key intermediate is envisaged to be octa-1,2,4,6,7-pentaenes formed upon electrocyclic ring opening of the starting material.
ISSN:0040-4039
1873-3581
DOI:10.1016/S0040-4039(00)73703-8