Phase-transfer catalysts can be used to transfer almost any anion into almost any organic liquid. When high temperatures are required for a reaction, a thermally stable phase-transfer catalyst can be used to transfer catalytic quantities of an anionic catalyst.
Tetraphenylphosphonium phenolate was used at a level of 0.02 wt% in the preparation of polyphosphonates from bisphenol A, methylphosphonic acid diphenyl ester and a crosslinker at 250-300 deg C.
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Cyclic carbonates are useful in the safe synthesis of non-isocyanate polyurethane resins (avoiding the use of phosgene). This patent describes the very efficient reaction of epoxides with carbon dioxide to form cyclic carbonates using phase-transfer catalysis.
The optimum catalyst system for the reaction of epoxides with carbon dioxide to form cyclic carbonates was found to be tetrabutylammonium bromide (TBAB) with cobalt diacetate tetrahydrate and triphenylphosphine. As can be seen in the diagram, a conversion of >99% was achieved with 1,4-butanediol diglycidyl ether as the substrate.
The presence of the phase-transfer catalyst was found to be the most crucial catalyst component. When TBAB was used without triphenylphosphine and without the cobalt catalyst, the conversion was 67%, presumably due to ring opening of the epoxide with bromide and subsequent attack of the alkoxide on carbon dioxide. When TBAB was used with triphenylphosphine and no cobalt catalyst, the conversion was essentially the same at 68%. However, when the cobalt catalyst was used without TBAB and without triphenylphosphine, the conversion was 0%. When all three catalyst components were used, >99% conversion was achieved.
It is interesting to note that phase-transfer catalysis could very likely be used to produce the starting material by hydrogen peroxide epoxidation of 1,4-butadiene. This reaction was not mentioned in the patent.
If your company needs help in choosing the most effective phase-transfer catalyst for reactivity, safety and processing to achieve the highest profit, now contact Marc Halpern of PTC Organics to explore how we can work together to improve your process performance from development to commercialization.
We found this perfluorooctyl quat salt, commonly known as FC-134, highlighted in a patent that issued this month entitled “Phase-transfer catalytic colour fixation processing method for textile.” See Long, J.; Xu, H.; Cui, C.; Chen, F.; Wei, X.; (Soochow University) US Patent 9,739,010, 22-Aug-2017
Sometimes, people confuse surfactant quats with phase-transfer catalyst quats (we wrote an article about this more than a decade ago shown at http://phasetransfer.com/PTCnotSurfactant.htm; note that the E-mail address and physical address shown in the article are no longer valid).
According to the patent, FC-134 was used to “notably improve the nucleophilic reactivity of functional groups on fibres in hydrophobic supercritical carbon dioxide, and has the advantages of improving the fixation efficiency of disperse reactive dyes on textiles, shortening the processing time and so on, even with simple process and easy operation.”
If the mechanism involves a nucleophilic reaction, then there is a chance that FC-134 is acting as a phase-transfer catalyst that transfers and activates a nucleophile into an non-polar phase. Supercritical carbon dioxide is a highly non-polar liquid that is effective in PTC applications such as those impressively developed and studied in great detail by Charles Liotta and Charles Eckert at Georgia Tech. However, given the unmistakable hydrophilic head-hydrophobic tail structure of the quat, there is a chance that the mechanism of activity is that of a surfactant and maybe less so that of a phase-transfer catalyst.
If you need help choosing a phase-transfer catalyst for a commercial process, now contact Marc Halpern of PTC Organics.
The primary use of tetramethylmmonium hydroxide (TMA OH) is as a KOH-replacement in the manufacture of semiconductors for the chip industry, however it has been used as a phase-transfer catalyst in certain applications since PTC was discovered a few decades ago. With a C# of 4 and a q-value of 4.00, tetramethylammonium is the quat cation with the most accessible positive charge on the nitrogen atom and is also the lowest formula weight quat. These properties make TMA OH among the least optimal quats for many PTC applications, but not always.
TMA cannot undergo Hofmann Elimination, which is the most common mechanism of decomposition of ammonium quats under basic conditions. Thus, TMA OH is more stable than other tetraalkylammonium hydroxides. This is a MAJOR advantage for certain PTC applications that require both base and high temperature.
One way to overcome the low organophilicity of TMA OH is to use a polar solvent and this is sometimes used in PTC applications.
This month, the use of TMA OH was reported, not as a phase-transfer catalyst, but as a base used stoichiometrically in the coupling of aniline with nitrobenzene to produce 4-nitrodiphenylamine, an intermediate for 4-aminodiphenylamine [Nandi, C.; Gangal, N.; Purohit, P.; Ketkar, V.; Kashelikar, D.; (Nocil Ltd) US Patent 9,708,243, 18-Jul-2017].
If your company needs to optimize the choice of phase-transfer catalyst to increase profit by achieving low-cost high-performance green chemistry, now contact Dr. Marc Halpern of PTC Organics.
The patent WO 2011/104089 describes the chiral PTC addition of hydroxylamine to alkenes to produce optically active isoxazolines. The inventors were very thorough and screened 14 quininium chiral phase-transfer catalysts under dozens of reaction conditions and achieved up to 90% ee and 88% yield.
The patent also describes the procedures for the synthesis of eight of these quininium phase-transfer catalysts. Even if you’re not interested in the synthesis of optically active isoxazolines, you should add this patent to your files for the synthesis of these chiral quats.
This is a very well researched Syngenta patent and the inventors are Nicholas Mulholland, Edouard Godineau, Jérôme Cassayre, Peter Renold, Myriem El Qacemi and Guillaume Revol.
At Informex 2017, opposite the Corning booth highlighting microreactor technology was an intriguing startup company Zaiput and its founder Andrea Adamo (shown in the picture).
The unit shown in the picture is a phase separation pilot unit that can separate up to about 200 mL/min of two liquid phases. It is fun to watch it in action.
The key of this phase separator is an organophilic PTFE membrane that allows organophilic liquids to pass through while rejecting polar aqueous phase. The cost of the membrane is low enough that it can be replaced when it fouls or otherwise experiences low efficiency.
One can envision the use of such a phase separator for phase-transfer catalyst recovery and recycle in a single step or in multiple countercurrent extractions
One can also envision the combination of PTC with microreactors and this phase separation unit for performing multiple consecutive PTC reactions using a single organic phase with an organophilic phase-transfer catalyst and multiple aqueous phases containing various nucleophiles. In other words, one could perform a rapid efficient PTC cyanide/chloride exchange of a benzyl chloride derivative in a microreactor, separate the phases with this phase separator, feed the organic phase containing the benzyl cyanide derivative and phase-transfer catalyst into a second microreactor that would perform a PTC C-alkylation of the intermediate followed by a second phase separation, feed the organic phase containing C-alkylated benzyl cyanide derivative and phase-transfer catalyst into a third microreactor where a PTC hydrolysis would be performed to produce a C-alkylating phenylacetate, which would be separated by a third phase separator.
After the final step, the C-alkylated phenylacetate would be located in the aqueous phase and the organic phase containing the phase-transfer catalyst could be recycled back into the first cyanide/chloride exchange reactor.
As we noted in this month’s PTC Tip of the Month, PTC and microreactors are a solution in search of a problem. When combined with the Zaiput phase separator, there is a great business opportunity for a chemical manufacturer or startup.
Please contact Marc Halpern of PTC Organics If you are aware of a chemical challenge, especially one that requires high selectivity or high productivity or short heat history and/or multiple consecutive PTC reactions that involve strong base reactions, nucleophilic substitutions, oxidations and/or reductions. We will be happy to sign a CDA and explore development and commercialization.
A simple synthetic procedure is provided for the quinidinium salt cited in the title. It is usually worthwhile saving such procedures for future reference. The procedure for the synthesis of N-(4,5-dimethoxybenzyl-2-nitrobenzyl) quinidinium bromide is shown below, as described in Adamo M.; (Royal College of Surgeons in Ireland) US Patent 9,593,071, 14-Mar-2017.
To a suspension of quinidine (650 mg, 2.0 mmol, 1.0 eq.) in THF (12.0 mL) 1-bromomethyl-4,5-dimethoxy-2-nitro-benzene (0.31 mL, 2.6 mmol, 1.3 eq.) was added. The resulting mixture was heated at 60 C for 16 h. The reaction was diluted with dichloromethane (10 mL) and washed with water (3×15 mL). The organic phase was dried over sodium sulfate and the solvent evaporated under reduced pressure. The crude material was purified by column chromatography (chloroform/methanol 95:5) affording the title compound as a purple solid (650 mg, 90% yield).
If you need to optimize the choice of phase-transfer catalyst for your commercial process, now contact Marc Halpern of PTC Organics Inc.
Tetramethylammonium nitrate can be combined with triflic anhydride to form a “nitronium triflate” that acts as a nitrating agent that is quite selective for a variety of aromatic rings including heterocycles (see: J. Org. Chem., 2003, 68, 267). In the reaction shown here from a March 2017 patent, TMA nitrate is used with triflic anhydride to selectivity nitrate an isoxazole. While not used catalytically, one may be able to envision considering catalytic tetramethylammonium chloride with stoichiometric inorganic nitrate for certain applications.
Always make sure to perform hazard operations analysis before performing any type of nitration reaction.
Now contact Marc Halpern of PTC Organics to choose the optimal phase-transfer catalyst for your commercial PTC process or industrial PTC process in development.
For those of you already familiar with the various generations of chiral phase-transfer catalysts, you may think you recognize the structure of the chiral phase-transfer catalyst shown here as belonging to the family of N-anthracenylmethyl cinchona alkaloid quats. However, on close examination, you notice that there is a nitrogen atom on the middle ring, making this an acridinylmethyl quat. The cinchona alkaloid is quinine since the hydroxyl is in a R-configuration (the S-configuration is quinidine) and there is a methoxy on the quinolone ring.
Acridinylmethyl quininium bromide was used in an interesting addition reaction of hydroxylamine to the double bond of a chalcone and chiral ring closure. Three points of interaction are required for the best chiral recognition and when looking at the structures of the starting material and chiral phase-transfer catalyst, it is not hard to envision 2 pi-pi interactions and one hydrogen bonding interaction between the chiral phase-transfer catalyst and the starting material.
Contact Marc Halpern of PTC Organics if your company can benefit from expert choice of phase-transfer catalyst for commercial PTC applications.
Methyl trioctyl ammonium trifluoromethanesulfonate was screened with other onium salts in adhesive compositions with cyanoacrylic esters. Ishizaki, K.; Ando, Y.; (TOAGOSEI) US Patent 9,458,361, 04-Oct-2016
The reason for using counteranions such as trifluoromethanesulfonate instead of chloride was to assure that the anion does not initiate polymerization, thus even mildly nucleophilic anions should be avoided.
If you need help choosing the most effective phase-transfer catalyst for your commercial PTC application, now contact Marc Halpern of PTC Organics Inc., the industrial phase-transfer catalysis experts.
