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From Phenyl Chlorides to α,n‑Didehydrotoluenes via Phenyl Cations. A CPCM–CASMP2 Investigation
journal contribution
posted on 2013-04-19, 00:00 authored by Davide Ravelli, Stefano Protti, Maurizio Fagnoni, Angelo AlbiniCalculations
with the complete active space self-consistent field
(CASSCF) method were carried out for rationalizing the photochemical
generation of the three isomeric didehydrotoluenes (DHTs) from the
corresponding (n-chlorobenzyl)trimethylsilanes. Moreover,
the original CASSCF energies were corrected through the introduction
of the dynamic electron correlation term (at the MP2 level) and of
an appropriate solvent model (CPCM). The work demonstrated the viability
of intersystem crossing (conical intersection located) leading to
the lowest lying triplet state of the silanes that fragments to give
the corresponding triplet phenyl cations. The para- and ortho-isomers desilylate directly from such
states of radical/radical cation character and yield the corresponding
DHTs in their triplet state. Different from the other isomers, the meta-cation has a radical/radical cation structure in both
spin states and thus two potential accesses to the different spin
states of the corresponding DHT.