Origins of the Regioselectivity in the Lutetium Triflate Catalyzed Ketalization of Acetone with Glycerol: A DFT Study

We describe DFT computations that address the regioselective preference toward the five-membered ring product 1,3-dioxolane (solketal) over the six-membered-ring product (1,3-dioxane) during Lu(OTf)3-catalyzed ketalization of acetone with glycerol. When ketalization occurs via the internal (secondary) −OH group of glycerol, only solketal production should be possible due to the symmetry of the intermediates. Ketalization via the terminal −OH group of glycerol is predicted to occur in a different manner than the conventionally proposed ketalization mechanism. A constrained hemiketal intermediate is invoked to explain the selectivity for solketal formation.