Regioselectivity of the Claisen rearrangement of meta- and para-substituted allyl aryl ethers

The regioselectivity of the Claisen rearrangement with different meta-substituted and meta- and para-substituted allyl phenyl ethers was investigated. The main results were that in meta-substituted Claisen rearrangements the regioselectivity depends roughly on the electronic nature of the substituent, with electron donating groups favoring migration to the further from the meta-substituent while electron withdrawing groups favor migration towards the meta-substituent. Different para-substituents were tested with two meta substituents, Me, and Cl. Most of the para-substituent tested had a clear effect on the product ratio, in all but one case enhancing the proportion of the major product favored by the meta substituent. Population analysis was performed with Mulliken, Löwdin, Hirshfeld, and natural population analysis to analyze the influence of the substituents on the atomic charges on the reaction sites. It was observed that the atomic charge on the carbon that forms the major isomer is of higher negativity than the atomic charge on the carbon that forms the minor isomer.