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Fluoro‐Ene Reaction Versus [2+2] Cycloaddition in the Thermal C 2 –C 6 Cyclization of Enyne‐Allenes: An Experimental and Theoretical Investigation
Author(s) -
Cinar M. Emin,
Vavilala Chandrasekhar,
Jaquet Ralph,
Bats Jan W.,
Schmittel Michael
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201402438
Subject(s) - chemistry , cyclobutene , diradical , enyne , ene reaction , cycloaddition , fluorine , exothermic reaction , pericyclic reaction , computational chemistry , cyclobutane , exergonic reaction , medicinal chemistry , reaction mechanism , photochemistry , organic chemistry , singlet state , catalysis , ring (chemistry) , physics , nuclear physics , excited state
A series of fluoroalkyl‐substituted enyne‐allenes have been synthesized by a new route with the aim of elucidating the possibility of a fluoro‐ene reaction via an intermediate fulvenyl diradical generated in the thermal C 2 –C 6 (Schmittel) cyclization reaction. As a result of the strong C–F bond, fluorine atom transfer was not observed. Instead, 1 H ‐cyclobuta[ a ]indenes were formed in good yields despite the high strain energy. DFT calculations at the B3LYP level of theory indicated that although the fluoro‐ene reaction is the most exothermic reaction available, cyclobutene formation is kinetically favored over the [1,5]‐fluorine shift by 5–15 kcal mol –1 in various model compounds.