We commend the inventors for recognizing that phase-transfer catalysis excels in performing specialty esterifications. We further commend the inventors for recognizing that solid-liquid PTC conditions are most likely to provide good results for the reaction shown in the diagram.
PTC esterifications are often performed at temperatures significantly higher than room temperature and one of the techniques to reduce the temperature is to use PTC-iodide co-catalysis. The inventors chose tetrabutylammonium iodide as the phase-transfer catalyst and this is a very reasonable choice that was likely crucial to achieve high conversion at room temperature.
However, if this reaction would progress to scale up, we would change a few of the process parameters chosen.
First, we would not choose acetonitrile as the solvent. We would choose a less polar solvent that is immiscible with water to facilitate workup on a large scale.
Secondly, we would choose to use a phase-transfer catalyst that is much less expensive than tetrabutylammonium iodide, such as tetrabutylammonium bromide and combine it with a small amount of potassium iodide. The combination of TBAB/KI is usually much less expensive than purchasing TBAI itself and this combination functions just as well as TBAI due to the much higher affinity of quat cations for iodide versus bromide, usually by more than an order of magnitude. We teach this in the 2-day course “Industrial Phase-Transfer Catalysis.” Has your company brought this course in-house in the last decade? If not, click here.
Thirdly, we expect that optimization studies would show that the amount of TBAB/KI could be greatly reduced from 10 mole% catalyst loading, perhaps down to 0.5 mole% to 2 mole%.
Now contact Marc Halpern of PTC Organics when you need to achieve the highest performance of your PTC process while minimizing your process R&D development time and cost.
