Visible Light-Induced\nRegioselective <i>E</i> to <i>Z</i> Isomerization\nof Polarized 1,3-Dienes: Experimental\nand Theoretical Insights

The stereocontrol of <i>E</i> → <i>Z</i> isomerization on a (1<i>E</i>,3<i>E</i>)-diene,\ninstead of a simple alkene, can be more challenging due to the increased\nnumber of isomerization possibilities. Herein, we report visible light-mediated\nregioselective (1<i>E</i>,3<i>E</i> → 1<i>E</i>,3<i>Z</i>) isomerization of (1<i>E</i>,3<i>E</i>)-diene. The reaction conditions are mild and\neasy to apply and can be applied to a wide range of substances, with\nan excellent yield and selectivity (90:10). It is evident from the\ncrystal structures that the cause of regioselectivity for the isomerization\nof 1,3-diene may not be limited to 1,3-allylic strains; CH−π\ninteraction may also play a vital role. Computational studies suggest\nthat this regioselective photoisomerization is a thermodynamically\nfeasible process and requires the accumulation of spin density on\nthe modified double bond for the transformation to occur.