The C2-chiral environment of L6 can be represented by a quadrant diagram, in which the regions where the ligand's methyl groups are oriented towards the substrate are highlighted in grey (Figure , structures displayed in SI). In TS3, C-C bond formation between allyl and tolyl groups occurs via rotational motion of these groups into a less hindered quadrant (Figure , black arrow), whereas for TS4, the opposite is true (Figure , orange arrow). The opposite sense of motion required for each TS relative to the catalyst's chiral pocket gives rise to the enantioselectivity. In terms of regioselectivity, we observe that the cationic  3 -coordinated Rh-centre shows much stronger coordination to the terminal allylic position, with terminal vs. internal Rh-C distances of 2.08 vs. 2.91 Å (in int1). In the RE TSs that form linear products, this coordination is necessarily disrupted (2.26 and 2.33 Å in TS5 and TS6) compared to the more favorable branched pathway (2.12 Å in TS3). The TS geometries at RE revealed that the bulk of allylic part (R = Ph, t Bu, Figure ) pointed away from the metal centre and the ligand, consistent with the transformation showing high regio-and enantio-selection across a wide range of allylic substrate including ones bearing t Bu group such as 54 and 55. Computed RE TSs with 55 show similar geometries to those shown above (see SI), suggesting a common enantiocontrol mechanism among these substrates.