Beilstein J. Org. Chem.2019,15, 1475–1479, doi:10.3762/bjoc.15.148
considered as a prototype for a 2e-4c Woodward–Hoffmann frozen transition state. The planar rectangular shaped structure 2 with a 2e-4c bond was found not to be a minimum.
Keywords: cyclobutane dication; 2e-4c bond; frozen transition state; Woodward–Hoffmannrule; Introduction
The protonated hydrogen
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Graphical Abstract
Scheme 1:
Examples of 2e-3c and 2e-4c bonded structures.