Cyclobutane dication, (CH₂)₄²⁺: a model for a two-electron four-center (2e-4c) Woodward–Hoffmann frozen transition state

• G. K. Surya Prakash and
• Golam Rasul

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–Hoffmann rule; Introduction The protonated hydrogen

• levels shows that the cyclobutane dication, (CH2)42+ (1), a prototype for a 2e-4c Woodward–Hoffmann frozen transition state, is a viable minimum on its potential energy surface. The structure contains formally two tetracoordinate and two pentacoordinate carbons. It resembles a complex between two