While our calculations indicate that increasing the number of Bpin units in 4 and 6 lowers the triplet energy compared to gem-diborylalkenes 1, making them potentially more reactive towards the EnT process, it remains unclear whether they can still undergo cycloaddition reactions. This uncertainty arises from the increased steric hindrance imposed by the bulkier Bpin groups attached to the double bond, which may render the double bond (e.g. biradicals II-III) to be less accessible for the required olefin's approaching during the cyclization event in II-2 and III-2 (Figure ). To this end, we attempted the [2+2]-cycloaddition of 1,1,2-triboryl-2-phenylethene 4a under the standard reaction conditions, with styrene 2a (Figure ). Remarkably, the reaction forged the tri-borylatedcyclobutane product (5a) in 40% yield for the major anti-diastereomer. Accordingly, other derivatives of styrene 2b, 2d, and 2s were tested, resulted in the formation of the desired cyclobutane products 5b-d with similar levels of selectivity and moderate yields (Figure ). Substituted arylated triborylalkenes 4b-d were also compatible in this reaction, providing the tri-borylated cyclobutane products 5e-i with moderate yields. Of note: the structure of tri-borylated cyclobutane product 5c was determined by X-ray crystallographic analysis (please see the X-ray structure of 5c in Figure ). The relative structures of 5c and 7b were confirmed by X-ray crystallography (please see Supporting Information for details), additionally the relative configurations of 5a-i were determined by 2D-NMR NOESY studies (see Supplementary pages S258-268). The dr (anti and syn) = diastereomeric ratio of 5 was determined by crude 1 H-NMR. Of note: Yields of isolated products 5a-i are given to the major anti-isomer which was isolated by column (we were unable to isolate the minor syn-isomer). Bpin=pinacolato-boron. DCE = 1,2-Dichloroethane. fac-Ir(ppy) 3 is fac-Tris(2-phenylpyridine)iridium(III). r.r. = regioselectivity ratio. Yields of isolated products are given.