Theoretical assessment of the viability of thermal [2+2] processes for formation of plumisclerin A

Results from density functional theory calculations on a proton-promoted [2+2] cycloaddition to form plumisclerin A's cyclobutane ring are described. On the basis of these results, it is proposed that protonation allows for an energetically viable stepwise cycloaddition that provides an alternative to photochemical cyclobutane formation.