Tetraoctylammonium phosphotungstate was used as a phase-transfer catalyst for the oxidative desulfurization of diesel according to US Patent 9,499,751 that issued 22-Nov-2016.
Tetraoctylammonium phosphotungstate was reported to be produced by dissolving sodium tungstate dehydrate in 30% hydrogen peroxide, adding 85% phosphoric acid, diluting with water then adding a solution of tetraoctylammonium chloride in methylene chloride. The organophilic tetraoctylammonium phosphotungstate distributes into the methylene chloride phase that is evaporated to yield the product.
If you need help choosing the best phase-transfer catalyst for your commercial PTC process in development or in production, now contact Marc Halpern of PTC Organics to achieve high-performance low-cost green chemistry.
Tetrabutylammonium oxone (peroxymonosulfate; HSO5-) was reported used in US Patent 9,493,511 (15-Nov-2016). Bu4N HSO5- was used stoichiometrically to oxidize a thioether to a sulfone. Peridoate was used to oxidize the thioether to the sulfoxide.
A less expensive alternative to using stoichiometric tetrabutylammonium peroxymonosulfate may be to use catalytic tetrabutylammonium hydrogen sulfate with stoichiometric potassium peroxymonosulfate. We teach this in our 2-day course on Industrial Phase-Transfer Catalysis. As always, conduct a fully competent hazard operations analysis before using PTC for oxidations of any type.
If you need help choosing a phase-transfer catalyst for a commercial PTC process, now contact Marc Halpern of PTC Organics Inc. to explore working together to achieve your commercial profit goals.
Tetrabutylammonium bis(fluorosulfonyl)imide, [Bu4N+(FSO2)2N-], is used as an ionic liquid, electrolyte, Lewis acid catalyst and in synthesis. The Bis(fluorosulfonyl)imide anion has been found to be useful as an esterification catalyst and as a polymerization catalyst for cationically-sensitive monomers such as epoxy resins.
A patent issued this month reports the improved synthesis of this tetrabutylammonium salt. Johnson, M.; (Trinapco) US Patent 9,475,764, 25-Oct-2016
Choosing a phase-transfer catalyst can sometimes by tricky. Contact Marc Halpern of PTC Organics Inc. to assure choosing the best phase-transfer catalyst for your commercial application inn production or in development.
When working with active alkylating agent, especially benzyl halides and allyl halides, one can often produce an effective quaternary ammonium phase-transfer catalyst by adding a trialkylamine to the alkylating agent forming the PTC in-situ or in advance.
In the patent shown here, the inventors used tributylamine to quaternize methylallyl chloride that was the alkylating agent to etherify a phenol followed by a Claisen rearrangement. The methylallyl chloride served as both alkylating agent for the etherification and source for the alkyl group of the in-situ PTC quat.
An interesting and practical aspect of forming in-situ quat salts as phase-transfer catalysts from benzyl chloride or allyl chloride derivatives is that if they decompose by nucleophilic attack of the nucleophile present in the PTC system, they actually form the desired benzylated or allylated product and liberate the triakylamine that can requaternize to form more phase-transfer catalyst. This is not only elegant, it saves money since tributylamine is less expensive than TBAB. In fact, this in-situ phase-transfer catalyst was compared to TBAB in this patent and they had similar performance.
If you can benefit from optimal choice of phase-transfer catalyst, now contact Marc Halpern of PTC Organics Inc. to explore collaborative consulting to achieve the highest performance lowest cost processes for your company.
It is rare to see tetrabutylammonium azide reported in the literature but this week, it appeared twice in US Patent 9,422,314 (23-Aug-2016). In Scheme 21 of this patent, tetrabutylammonium azide was used in the conversion of a cyclic trans 1-azide 2-mesylate to a cis-bisazide. It is interesting that in the previous step, which was a ring opening of an epoxide to a trans azido alcohol followed by conversion to the trans azido mesylate, the inventors used sodium azide and polyethylene glycol and not tetrabutylammonium azide. One would think that they would have used the same azide (either sodium or tetrabutylammonium) for both steps. Perhaps the ring opening was easier than the displacement of the secondary mesylate. In Scheme 25 of the patent, the inventors used tetrabutylammonium azide to displace a secondary tosylate on an open alkyl chain.
Overall, we do not recommend storing quat azides in the lab since they can potentially form alkyl azides that are unstable and potentially explosive. One should particularly avoid using quaternary ammonium salts that contain methyl groups or ethyl groups in the presence of azide since the potential formation of methyl azide or ethyl azide are very dangerous.
Before using phase-transfer catalysis for any azide reaction, make sure to do proper safety testing, for example DSC analysis, to assure that even small scale reactions can be performed safely.
If you need help to choose the best phase-transfer catalyst to make sure you don’t leave unrealized wasted profit on the table, now contact Marc Halpern of PTC Organics Inc.
Polyethylene glycols are “complexant” phase-transfer catalysts that act by complexing with cations such as sodium ion and potassium ion through the polar non-bonding electrons on the multiple oxygen atoms. Since sodium cation and potassium cation are part of a salt, the complex [PEG-NaX] moves as one and can distribute between aqueous and organic phases.
PEG 2000 has a solubility of about 60% in water at 20 deg C, but can also dissolve in organic solvents due to the many ethylene groups on the molecule (an average of 90 carbon atoms). PEG’s are on the FDA’s GRAS list (compound Generally Recognized As Safe) which suggests lower toxicity than quaternary ammonium phase-transfer catalysts.
A question sometimes asked about high molecular weight PEG’s is ‘how many alkali metal cations bind to one molecule of PEG?” This is important to attempt to estimate about how much PEG 2000 might be required to be an effective phase-transfer catalyst. The basis for the question is that it takes about 5-6 oxygen atoms in a crown ether, that is essentially a cyclic PEG, to complex with one Na cation or potassium cation. There are about 45 oxygen atoms on average in molecules/oligomers of PEG 2000! So, PEG 2000 might be efficient or might be very inefficient. The answer is that sometimes only one NaX or KX on pair can be transferred by one high MW PEG molecule and sometimes several NaX or KX ion pairs can be transferred by a single high MW PEG molecule. Each case is different based on the application, the solvent used, the identity of X (the anion we are trying to transfer and react) and possibly other factors. The easiest way to find out is to compare the performance of PEG 2000 with the performance of PEG 400 in the actual PTC system.
If you are looking to consider less expensive alternatives to quaternary ammonium phase-transfer catalysts and/or that contain no nitrogen atoms, contact Marc Halpern of PTC Organics to explore how we might work together to achieve your company’s process development goals.
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A very impressive patent issued this week that conclusively shows greatly improved performance for some intramolecular C-alkylations achieved by quaternizing the quinoline nitrogen of quaternary cinchona alkaloid phase-transfer catalysts.
In one example (see Table 1 in the patent), the use of 3 mole% of the mono-quat shown gave 58% ee and 80% conversion when only 0.3 mole% of the bis-quat derived from that mono-quat gave 92% ee and 100% conversion. This is a patent worth reading!
If you need expert help in choosing a phase-transfer catalyst for your commercial PTC application in development or in need of optimization, now contact Marc Halpern of PTC Organics to explore integrating our highly specialized PTC expertise with your commercial and process development goals.
Trihexyl tetradecyl phosphonium chloride is a highly organophilic quat with a C# of 32 and modified q-value of 0.57 beyond the looseness of the ion pair due to the large polarizable phosphorous atom bearing the positive charge.
US Patent 8,920,673 shows how liquid-liquid ion exchange can be used to replace chloride in trihexyl tetradecyl phosphonium chloride with various carboxylates, phenoxides and other organic anions with just one extraction. These materials are used as room temperature ionic liquids.
Typically liquid-liquid ion exchange to replace chloride or bromide in quats is performed by multiple extractions or countercurrent extraction. When the anions replacing chloride are organophilic enough, their affinities for the organophilic quat are strong enough be effectively displace the chloride anion in just one extraction.
As we teach in the 2-day PTC course “Industrial Phase-Transfer Catalysis,” the relative affinities of various anions for quats is often important to optimize commercial PTC processes.
It makes sense that if one wants to transfer and react an organic dianion from an aqueous phase to an organic phase using phase-transfer catalysis, one could use a bisquat dication that would match the distance between the charges on each molecule for effective electrostatic interaction.
This phase-transfer catalyst, bis(tributyl)-1,6-hexylenediammonium dibromide, was designed for the reaction of the disodium salt of bisphenol A with nitrophthalimide. The two anionic centers of bisphenoxide are located on opposite ends of the molecule and are separated by two rigid rings and another carbon. One might expect good association between the dianion and dication if the approximate distance between the two positive charges on the bisquat were approximately the same as the two negative charges on the bisphenoxide, accounting for flexibility and rotation of the alkyl chain of the bisquat.
The inventors chose spacers of 4, 6 and 10 carbons between the two quat cation centers of the bisquat. They found that 4 carbon atoms is too short for bisphenoxide. They found that spacers of 6 and 10 carbon atoms were very effective and had similar performance, achieving 98% yield after 2 hours using 1 mole% bisquat as phase-transfer catalyst.
They also found that quarternizing the dibromoalkane with trihexylamine instead of tributyl amine, did not increase reactivity. As a result they chose bis(tributyl)-1,6-hexylenediammonium dibromide as the best choice for combination of spacer, organophilicity/accessibility of the two positive charges and cost for bisquat for the target reaction.
The bisquat is made by simply mixing 1,6-dibromohexane with 2 equivalents of tributyl amine in acetonitrile at reflux for 24 hours, stripping off the acetonitrile and recrystallizing from toluene. This procedure is similar to that used to produce many quats.
In 1983, I was finishing my work on phase-transfer catalysis for my Ph.D. thesis and I synthesized several bisquats for screening but never tested them (my supervisor thought that the 15 PTC publications I had during my graduate research was more than enough to proceed to my post-academic career). I was pleased when I saw this patent and similar publication in 1985 that showed that the bisquat-dianion concept worked well.
Now contact Marc Halpern of PTC Organics if you need help choosing the best phase-transfer catalyst to squeeze the most performance out of your commercial PTC process in development, scale up or production.
This phosphazenium catalyst is easily produced by the reaction of tetramethyl guanidine with phosphorous pentachloride followed by treatment with an hydroxy group-type anion exchange resin (AMBERLITE IRA 410 0H) as shown in the diagram.
This catalyst was developed specifically for alkoxylations and there are numerous examples of producing polypropylene oxide. Advantages of using this catalyst include high conversion, low polydispersity, no odor, avoiding the use of zinc, cobalt or other metal-based catalysts, and much lower catalyst loading relative to KOH for example.
If you want to optimize the choice of catalyst for a PTC application in development, scale up or production, now contact Marc Halpern of PTC Organics to explore integrating highly specialized expertise in industrial phase-transfer catalysis with your company’s commercial goals.
