Metal Removal

Removing residual metals from post reactions can be a major issue. The toxic nature of transition -metals has led to the reduction of tolerated residual concentration in active pharmaceutical ingre-dients (APIs) to single digit ppm. However, many important key steps, such as coupling reactions (Suzuki, Heck, Stille, Sonogashira, etc), ring closing metathesis (RCM), and hydrogenation, still require the use of metal catalysts.

Purification of the API from remaining metal by traditional methods (chromatography, activated -carbon, distillation, recrystallisation, ultrafiltration, or reverse osmosis) often leads to problems such as high costs, time consuming, low efficiency, and API losses. SiliCycle has developed an efficient alternative: SiliaBond^® Metal Scavengers.

These scavengers are made with SiliCycle's high purity silica gel: SiliaFlash^®, which does not suffer from polymers' shortcomings, (i.e.: limited choice of solvents, excessive -swelling, extensive washings, poor selectivity, and static charge).

SiliaBond Metal Scavengers have significantly improved the way APIs can be synthesized. Any metal containing catalyst can be used, even downstream, as there are efficient scavengers available for -metals such as Pd, Pt, Sn, Ru, Rh, Ni, Cr, etc. Treatment with Metal Scavengers will selectively reduce the metal concentration without affecting the API.

APPLICATION NOTES

SiliaMetS® Thiol
SiliaMetS^® Thiol (Si-Thiol) is a robust metal scavenger for a variety of metals including Pd, Pt, Cu, Ag and Pb under a wide range of conditions. It has been used in pharmaceutical processes up to the pilot plant scale. It is our most versatile metal scavenger and is the preferred metal scavenger for Pd(II), Cu, Ag, and Hg.
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SiliaMetS® Thiourea
SiliaMetS^® Thiourea (Si-THU) is a versatile metal scavenger for all forms of palladium and is widely used in the pharmaceutical industry. It works particularly well in organic solvents. It can also be used to scavenge Ag, Pt, Ru, Rh and Hg. Once complexed with a transition metal, it has been reported as being an effective catalyst.
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SiliaMetS® Cysteine
SiliaMetS^® Cysteine (Si-Cys) is the silica bound equivalent of the amino acid Cysteine. By attaching the molecule to the backbone via the amino group, the thiol group remains free and accessible for higher metal scavenging efficiency. It is a versatile metal scavenger for a variety of metals including Pd, Sn, Ru, Pt, Cu, Rh, Cd and Sc under a wide range of conditions and the preferred metal scavenger for tin residues.
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SiliaMetS® Dimercaptotriazine (DMT)
SiliaMetS^® DMT (Si-DMT) is the silica bound equivalent of 2,4,6-trimercaptotriazine (trithiocyanuric acid). It is a versatile metal scavenger for a variety of metals including Cd, Co, Ni, Pd, Pt, Rh, and Ru under a wide range of conditions and the preferred metal scavenger for ruthenium catalysts.

TMT has been reported to efficiently remove palladium and heavy metals by precipitation. Unfortunately, its solubility in organic solvents causes problem. SiliaMetS DMT solves this issue and almost all solvents can now be used.
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SiliaBond® Amine
SiliaBond^®Amine (Si-NH₂) is an effective scavenger of acid chlorides, sulfonyl chlorides, isocyanates and other electrophiles. Si-NH₂ has been shown to be effective metal scavenger and catalyst for Knoevenagel reactions. SiliaBond Amine is also used in chromatography as normal phase sorbent.
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SiliaBond® Amine nec
SiliaBond^®Amine (Si-NH₂) is an effective scavenger of acid chlorides, sulfonyl chlorides, isocyanates and other electrophiles. Si-NH₂ has been shown to be effective metal scavenger and catalyst for Knoevenagel reactions.SiliaBond Amine is also used in chromatography as normal phase sorbent.
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SiliaMetS® Diamine
SiliaMetS^® Diamine (Si-DIA) is a proven scavenger for metals and electrophiles. It scavenges acids, acid chlorides, anhydrides, aldehydes, isocyanates, and chloroformates as well as Pb, Ni, and Cd.
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SiliaMetS® Triamine
SiliaMetS^® Triamine (SiliaMetS WAX-3, Si-TRI) is effective for scavenging metals such as Pb, Co, Ru and Pd. Our screening studies have shown it to be the preferred scavenger for Pb. It can also be used as a scavenger for acid chlorides, isocyanates and other electrophiles.
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SiliaMetS® Imidazole
SiliaMetS^® Imidazole (Si-IMI) is a versatile metal scavenger for a variety of metals including Cd, Co, Cu, Fe, Ni, Pd, and Rh under a wide range of conditions and the preferred metal scavenger for iron catalysts.

SiliaMetSImidazole can also be used as an amine base in systems that are generally sensitive to basic conditions compared to other SiliaMetS supported bases.
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SiliaMetS® TAAcOH
SiliaMetS^® TAAcOH (SiliaMetS Triaminetetraacetic Acid) is a silica bound metal scavenger for Pd(0), Ni(0) and Cu. It is the supported version of EDTA in its free form. It is an effective scavenger for metals in low or zero oxidation states, which includes many of the most synthetically useful catalysts such as tetrakis-(triphenylphosphine)palladium(0).
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Testimonials

“The high quality nature of the columns and plates from SiliCycle has allowed us to achieve a level of reproducibility with our compound libraries that would be unheard of with any other production line.”
[Steven Marois, Boston University CMLD]

“Several of my teams have successfully employed SiliCycle resins to scavenge metals from APIs. The fact that these scavengers work so well allow us to employ Pd-catalyzed cross couplings as final steps in API synthetic sequences confidently, knowing that we will likely be able to reduce transition metal contamination to acceptable levels in the final drug substance.”
[Akin Davulcu, Bristol-Myers Squibb]

“BioVectra has been able to leverage its large scale chromatography capability with the technical and product capability of the SiliCyle team into the manufacturing of important oncology active pharma ingredients. We have been associated with SiliCycle since 1998, and look forward to working together on many new projects in the future.”
[Dale Zajicek, BioVectra]

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