Hydration of 1-Phenyl-1-Propyne in High-Temperature Water with Catalysis by Water-Tolerant Lewis Acids

We explore various aspects of alkyne hydration in high temperature water catalyzed by water-tolerant Lewis acids through experimentation with the hydration of 1-phenyl-1-propyne. Experiments comparing indium triflate, scandium triflate, ytterbium triflate, sulfuric acid, and hydrochloric acid indicate that indium triflate is the most active catalyst toward this reactive system of those tested. Experiments with quartz and stainless steel reactors in conjunction with quartz and stainless steel additive demonstrate that reactor material of construction has no appreciable effect upon the reaction. The reaction is first order in both catalyst and alkyne. We further determine the kinetic parameter k for four temperatures (150, 175, 200, and 225 °C), and find that the frequency factor is 108.8±0.3 L/(mol s) and the activation energy is 21.4 ± 0.6 kcal/mol for this transformation. This is the first example of alkyne hydration in high-temperature water catalyzed by water-tolerant Lewis acids.