(159g) Regioselectivity of Epoxide Ring Opening with Alcohols Using Lewis Acidic Zeolites and Nano-Zeolites

Epoxides are versatile intermediates that can be ring opened using different nucleophiles to produce a wide variety of valuable chemicals. The key challenge for this reaction is selectivity. Indeed, the ring opened epoxide can form oligomeric byproducts or can produce either a terminal ether or a terminal alcohol, resulting in low regioselectivity. Previous work with Bronsted acidic catalyst results in low regioselectivity. Higher regioselectivity has been observed for Lewis acidic catalysts such as Co-Salen and Co-Porphyrin, but these catalysts tend to deactivate. Intriguingly, Lewis acidic zeolites have been demonstrated for the water ring opening of epoxides to produce a diol. In this work, we will discuss the regioselective epoxide ring opening reaction with alcohols for Lewis acidic catalytic materials. Through comparing catalytic activities, it is found that Sn-Beta is more active than other similar Lewis acidic catalytic materials such as Sn-MFI and Sn-SBA-15. For all materials, high regioselectivity of >97% is obtained. With large substrates such as epoxy octane, diffusion limitations are encountered that can be overcome through creating zeolites with particle sizes less than 100 nm. These materials can be readily recycled while retaining high catalytic activity and selectivity. Hot filtration tests demonstrate that these catalysts are heterogeneous in nature and stable. These promising results induced us to examine the reaction mechanism using computational methods. DFT analysis demonstrates that the reaction mechanism involves the activation of the alcohol on the Lewis acidic catalytic site. The epoxide adsorbs on the activated alcohol, allowing the ring opening to proceed by the attack of a second alcohol. Overall, these materials represent highly active and selective catalysts for the conversion epoxide ring opening reaction.