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Ring Strain Effects in Enyne-Allene Thermolysis: Switch from the Myers-Saito Reaction to the C2-C6 Biradical Cyclization

✍ Scribed by Michael Schmittel; Jens-Peter Steffen; Dominik Auer; Michael Maywald

Publisher: Elsevier Science
Year: 1997
Tongue: French
Weight: 485 KB
Volume: 38
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(97)01393-2

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✦ Synopsis

The mode of the thermal cyclization of enyne-allenes 1 depends on ring strain effects: when the ene functionality is part of a benzene, cyclohexene or cycloheptene ring the novel C2-C6biradicrd cyclization is observed, while when it is part of a cyclopentene ring the Myers-Saito cycloaromatization is registered. @ 1997Elsevier ScienceLtd.

Recent results from our laboratory2'3and later from two other groups4'5have unambiguously established that the well-known Myers-Saito cycloaromatization6'7of enyne-allenes via biradical B can be completely replaced by a novel C2-C6cyclization as soon as aryl groups or sterically demanding substituents are affixed to the acetylene terminus. Mechanistic investigationss and DFT calculations indicate that the novel cycliration

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