A patent was issued this month that reported the use of tetrabutylammonium cyanide (US 10,053,435) for a cyanide-nitro displacement.
If this reaction would ever need to be scaled up, we would expect that we could save money by performing this reaction using catalytic TBAB and NaCN instead of tetrabutylammonium cyanide.
The focus of this patent was to replace the nitro group with a fluoride. Tetrabutylammonium fluoride was used as the fluoride source or as a catalyst with an alkali metal fluoride as the fluoride source.
Now contact Marc Halpern of PTC Organics when you need to optimize the choice of phase-transfer catalyst to reduce the cost of your commercial PTC process.
2-Hydroxypropyl trimethyl ammonium formate is one of several catalysts in the 2-hydroxyalkyl trialkyl ammonium quat series used for the trimerization of isocyanates to isocyanurates then formation of polyisocyanurates used as thermoset resins.
Strangely enough, some of these quats go by the tradename “Dabco TMR-x” wherein “x” is a number. This is strange since the compound commonly referred to by organic chemists as DABCO is a trialkylamine (not a quat salt) and is also a trimerization catalyst. 2-Hydroxypropyl trimethyl ammonium formate and other Dabco TMR quat salts were mentioned this month as catalysts in US Patent 10,030,094.
For general knowledge, polyisocyanurates are made from isocyanates and polyols and are different from polyurethanes in two ways: [1] the ratio of MDI (methylene diisocyanate) to polyol is higher in polyisocyanurates than in polyurethanes and [2] the polyol in a polyisocyanurate is a polyester-polyol whereas polyurethanes use polyether polyols (like polyethylene glycol).
This patent from UC Berkeley describes what appears to be a significant breakthrough in both phase-transfer catalysis as well as chiral phase-transfer catalysis.
The first report of an anionic phase-transfer catalyst that I recall was in the late 1970’s and it was based on a highly polarizable tetraarylborate anion that supposedly transferred a proton into an organic phase, then performed an acid-catalyzed reaction. However, the claims in that report were subsequently withdrawn. Over the years there have been occasional rare reports of various types of anionic phase-transfer catalysts but none seemed to enjoy wide application.
This patent describes an anionic phase-transfer catalyst that incorporates structures similar to the Maruoka chiral phase-transfer catalysts with the big difference being that instead of a nitrogen center forming a chiral quat, there is a phosphate center that when deprotonated forms an anion. This creates an organophilic chiral anion that is able to pair with and transfer a cation into a non-polar organic phase for reaction.
The examples in the patent focus on the transfer and reaction of the di-cation of “Selectfluor” (a trademark of Air Products and Chemicals) that is effective for a variety of fluorine reactions. We will highlight these reactions in future issues of the PTC Catalyst of the Month and we will also show some of these reactions in the 2-day course “Industrial Phase-Transfer Catalysis” that you can conduct in-house or attend in Philadelphia on October 2-3, 2018.
Tetraethyl ammonium bicarbonate was reported this month to be used as a base in acetonitrile and in DMF to control pH in fluorine-18 radiolabeling syntheses. Vasdev, N.; Rotstein, B.; Stephenson, N.; Liang; H.; (The General Hospital Corporation) US Patent 9,957,231, 01-May-2018. This patent also provides a reference for the use of this quat salt as a phase-transfer agent in the formation of [18F]fluoroarenes.
Learn to choose phase-transfer catalysts like an expert at the 2-day course “Industrial Phase-Transfer Catalysis” to be conducted in Philadelphia on Oct 2-3, 2018.
A patent just issued last week to Sachem, one of the most veteran manufacturers of high purity quaternary ammonium phase-transfer catalysts, that describes how to inhibit color formation of quat hydroxides in non-aqueous solvents (glycols). Sachem has been a leader in the commercial supply of quat hydroxides, especially those used in the manufacture of semiconductors.
Quat hydroxides that contain at least one ethyl or higher alkyl group, can undergo Hofmann Elimination. Quat hydroxides are relatively stable to this decomposition at room temperature, though decomposition is possible with extended shelf life if not stored in a cool environment. It is speculated that the amine liberated by this quat decomposition mechanism can oxidize when exposed to air over time and create color compounds.
Sachem inventors found that the addition of small amount of hydantoin (10-5000 ppm) to non-aqueous solutions of quat hydroxide (20 wt%-50 wt%) containing less than 0.5 wt% water, can effectively inhibit color formation. Engel, T.; Van Lier, A.; (Sachem) US Patent 9,944,853, 17-Apr-2018
It is important to note that hydantoin (imidazolidine-2,4-dione) has two active N-H bonds, so if the quat hydroxide is being used to perform base-promoted alkylations or other reactions that may be affected by active N-H groups, small amounts of impurities may be formed by the reaction of hydantoin with reaction components unless the hydantoin is removed prior to the reaction.
Now contact Marc Halpern of PTC Organics if your company needs expert input for choosing the optimal phase-transfer catalyst for your commercial PTC application.
Tris[2-(2-methoxyethoxy)ethyl]amine is a complexant phase-transfer catalyst that combines the effectiveness of cryptands and crown ethers with the open chain structure of polyethylene glycols.
First commercialized by Rhone Poulenc as TDA-1 in the 1980’s, this phase-transfer catalyst enjoyed many successful PTC applications, including some surprising ones like the Ullmann Reaction and even the Grignard Reaction. When Rhone-Poulenc discontinued TDA-1, PTC applications decreased.
Recently, we received information that tris[2-(2-methoxyethoxy)ethyl]amine may become available again commercially.
If your company would like to screen this highly effective phase-transfer catalyst for your processes in development, please contact Marc Halpern of PTC Organics.
Tertiary amines, such as DABCO, are often used as catalysts in the production of polyurethane foams that react polyols with isocyanates. Screening catalyst formulations is easy by measuring the height and consistency of the rate of foam rise after adding the isocyanate to a mixture of polyol, catalyst and blowing agent (e.g., pentane, not CFC) in a metal cup. Each catalyst system has advantages and disadvantages.
A patent issued this month (Burdeniuc, J.; Panitzsch, T.; Dewhurst, J.; (Evonik Degussa GmbH) US Patent 9,890,236, 13-Feb-2018) compares various catalysts for polyurethanes, including dimethyl diallyl ammonium pivalate with classical DABCO catalysts (tertiary amine). This quat salt gave consistent foam rise at a good rate similar to or better than the standard DABCO catalysts typically used, but quat salts are not volatile and therefore do not suffer from odors from tertiary amines such as DABCO. Diallyl dimethyl ammonium chloride is a low molecular weight quat salt (more moles per kg) made from inexpensive raw materials and the chloride is easily exchanged for pivalate, a sterically hindered carboxylate (an important factor of this invention).
Contact Marc Halpern of PTC Organics when you need help choosing a phase-transfer catalyst for a commercial PTC application.
It is rare to see secondary alkyl groups on quaternary ammonium salts. About 25 years ago, there was a report of a thermally stable quat salt containing isopropyl groups. So, it was interesting to see trimethyl-iso-propylammonium quats described in Kalb, R.; Kraynov, A.; (Proionic GmbH) US Patent 9,868,635, 16-Jan-2018.
The quat was synthesized by reacting dimethyl isopropyl amine with dimethyl carbonate in methanol (90 deg C for 7 days gave 99.9% conversion) to form trimethyl-iso-propylammonium methylcarbonate. The quat borohydride was obtained by ion exchange of the quat methyl carbonate with aqueous sodium borohydride at basic pH.
Trimethyl-iso-propylammonium borohydride is used as an ionic liquid for storing hydrogen. This is an interesting patent.
Contact Marc Halpern of PTC Organics when you need help choosing a phase-transfer catalyst for a commercial PTC application.
We have seen many patents claim many quaternary ammonium and phosphonium salts as phase-transfer catalysts. But this patent by L’Oreal cites 173 specific quats and diquats for pairing with anionic dyes and optical brighteners. It is interesting to browse the eight pages of quat structures shown. David; H.; (L’OREAL), US Patent 9,839,591, 12-Dec-2017
The properties of quaternary ammonium and phosphonium cations that make them good phase-transfer catalysts include the ability to pair with anions and make them lipophilic. The cationic nature and affinity for organic materials, leads to the combination of these quats with the anionic dyes and anionic brighteners resulting in chromatic, powerful and particularly fast coloration on keratin fibers and particularly lightening coloration via an optical effect on dark hair. It makes sense.
The invention relates to chiral imidodiphosphates and derivatives, which are suitable as chiral Bronsted acid catalysts, phase-transfer catalysts, chiral anions for organic salts, metal salts or metal complexes for catalysis.
The reaction shown is not a PTC reaction but it does illustrate how the twisted chiral structure can induce chiral recognition. As expected, when the stereochemistry of the catalyst is reversed, similar performance is achieved with the opposite enantiomeric composition. Catalytic examples were shown for 5-membered rings and 6-membered rings.
