This patent describes a high yield PTC C-alkylation performed under dilute liquid-liquid PTC conditions in a microreactor. A forced thin film microreactor (shown in the diagram at https://www.m-technique.co.jp/e/members/ulrea/kouzou.html) is different than many other microreactors. In most microreactors used with phase-transfer catalysis, the two liquids (aqueous phase and organic phase) are fed into in a static channel. In contrast, in a forced thin film reactor, the two liquids (aqueous phase and organic phase) are fed into a narrowing channel in which part of the channel surface is static and the other part of the channel surface is rotating.
The advantage of the forced thin film microreactor is claimed to be scalability without having to add too many microreactors in series as is commonly done with static microreactors.
For reasons not explained, performance is better when the aqueous phase containing the phase-transfer catalyst and NaOH is agitated for 15 minutes in a “Clearmix preparation apparatus” before being contacted with the organic phase. This seems surprising since the aqueous phase is quite dilute and both the NaOH and TBAB should be dissolved homogeneously without much effort or time. However, the results speak for themselves.
When the aqueous phase is prepared with the Clearmix apparatus (Table 1: Examples 1, 6, 7), the yields are 88% to 97% whereas when the “aqueous solution, which was manually agitated, was used after it was visually confirmed that the reacting agent was dissolved” (Comparative Example 1), the yield was only 51%. In all of these cases, the microreactor in which the PTC reaction was performed was a forced thin film type operating at the same flow rates and same rotation speeds of the rotating surface.
This patent should be studied by those of you who are combining the powerful advantages of phase-transfer catalysis with the powerful advantages of microreactors.
