Resolving the mechanistic origins of E/Z-selectivity differences for the ortho-aryl-Claisen [3,3]-sigmatropic rearrangement through DFT calculations

The mechanistic origins of E/Z-product selectivity differences for the synthetically important thermal ortho-aryl-Claisen [3,3]-sigmatropic rearrangement is resolved through a computational study. The formation of E- and Z-products has previously been proposed to occur as a result of reaction via different chair-like transition states or through chair- and boat-like transition states. Using DFT B3LYP/6-31G* calculations on a previously reported experimental system, it has been determined that differences in E/Z-product selectivities primarily arise by progression through different chair-like transition states.