We initiated our optimization probing the efficiency of diene 1 to undergo 2+2 cycloaddition with styrene 2 in the presence of a photocatalyst (Table ). Utilizing a lower energy sensitizer [Ru(dmbpy)3](PF6)2, afforded 2+2 adduct E-3 in appreciable yield and good regio-and site-selectivity (Entry 1). However, significant amounts of dimer 4 were generated, hindering the targeted reactivity. Implementing sensitizers of higher energy was detrimental, resulting in formation of geometrical alkene isomer Z-3 (Entries 2 to 4), while also compromising diastereoselectivity (See ESI for full details). Varying styrene equivalents had little effect in suppressing dimer formation (Entries and). Inspired by recent studies exploiting slow addition to mitigate homodimerization, 8e we next employed a syringe pump to carefully control the concentration of diene 1 (Entry 7). Pleasingly, this regulated the formation of dimer leading to excellent yields of 2+2 heteromer. Carrying out the reaction under an air atmosphere supported a triplet EnT process (Entry 8), while control reactions demonstrated that catalysis is operational (Entries 9 and 10). (kcal/mol) Having established conditions that promote the target reactivity we next set out to determine the scope and compatibility of the model system (Scheme 1). For all reactions assessed, site-, regio-and alkene E/Z selectivity was comprehensively in favor of one product. Our model reaction led to the generation of four diasteromers favoring an anti relationship between aryl and styrenyl substituents and anti for styrene and boron motif (3).