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How to Lose a Bond in Two Ways ― The Diradical/Zwitterion Dichotomy in Cycloaromatization Reactions
Author(s) -
Peterson Paul W.,
Mohamed Rana K.,
Alabugin Igor V.
Publication year - 2013
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.201201656
Subject(s) - diradical , chemistry , zwitterion , synapsis , dichotomy , computational chemistry , organic chemistry , molecule , epistemology , quantum mechanics , biochemistry , physics , philosophy , homologous chromosome , gene , singlet state , excited state
Cycloaromatization reactions decouple two electrons by breaking two π bonds to form only one σ bond and illustrate one of the most common mechanistic dichotomies in chemistry, namely the two ways of breaking a chemical bond: Zwitterionic or diradical. With a suitable choice of reaction conditions, substitution patterns, and catalysts, cycloaromatization processes can be redirected from the usual formation of a diradical towards a variety of zwitterionic pathways. This review illustrates the practical approaches for directing zwitterionic cycloaromatization reactions and lays the mechanistic foundations for the further development of this emerging field.