Herein we describe the EnT mediated 2+2 cycloaddition of conjugated organoboron systems proceeding with excellent site-selectivity, regioselectivity and diastereoselectivity (Figure ). The judicious choice of a low energy catalyst system mitigates "alkene scrambling" to limit reaction outcomes to a single geometric isomer. Systematic analysis of boron substituents unveils a clear relationship between boron species and compatible alkene coupling partners, while subtle modifications of the core scaffold enabled a divergent pathway to form preferentially 4+2 cycloadducts. Mechanistic probes revealed a counterintuitive geometric isomerization with opposite regioselectivity to that of 2+2 cycloaddition, leading to an in-depth computational study to determine the intimate links between spin density, reactivity and the origin of reaction divergence.