Dysprosium Catalysts

Dysprosium is a chemical element with the symbol Dy and its atomic number is 66. Dysprosium is a silver-white metal that can be cut with a knife due to its soft texture. Dysprosium in the elemental state has never been found in nature, although it exists in various minerals, such as xenotime. Natural dysprosium consists of seven isotopes, the most abundant of which is ¹⁶⁴Dy. Dysprosium is chemically stable in the air and only can be oxidized by air and water to form dysprosium trioxide at very high temperatures. Dysprosium compounds are mainly used as catalysts in the refining industry.

Applications:

Due to its mild nature, the compound containing dysprosium(DyCl₃ or Dy(OTf)₃) usually maintains its catalytic activity in the presence of lewis basic nitrogen groups, so it can be used as a catalyst to catalyze the chemical reactions of substances containing an N or O functional group. In addition, it can be used as a catalyst in protic or ionic liquids. DyCl₃ and Dy(OTf)₃ are catalysts suitable for green chemistry because their recycling is relatively easy.

• DyCl₃-catalyzed Friedel-Crafts alkylation:

Alkylation is critical for the formation of carbon-carbon bonds, and Friedel-Crafts alkylation is an important means of establishing carbon-carbon bonds. Dysprosium chloride is highlighted as the optimal alkylation catalyst. Take figure 1 as a example, this catalyst can be recovered and recycled easily, and maintained catalytic activity for all three reaction cycles.

Figure 1 The reaction schematic of DyCl₃-catalyzed Friedel-Crafts alkylation

• DyCl₃-catalyzed Mannich-type reactions:

The Mannich reaction is widely used as a valuable transformation in total synthesis. Using dysprosium chloride as catalyst can increase the yield. It is speculated that the dysprosium chloride generated a reducing medium, which suppressed the detrimental formation of I2, so the yield of this reaction was enhanced from 66 to 79%.

• Dy(OTf)₃-catalyzed DielseAlder and Povarov reactions:

In DielseAlder and Povarov reactions, Dy(OTf)₃ is considered as a favored catalyst. The reaction schematic is shown in Figure 2.

Figure 2 The reaction schematic of Dy(OTf)₃-catalyzed DielseAlder

• Dy(OTf)₃-catalyzed electrocyclizations:

The Nazarov cyclization is a prime example of such electrocyclization, and it is a route to obtain important and useful cyclopentenones. Lewis acids are widely employed as catalysts in Nazarov cyclization. The reaction schematic is shown in Figure 3.

Figure 3 The reaction schematic of Dy(OTf)₃-catalyzed electrocyclizations

• Enantioselective dysprosium-catalyzed alkylation:

The yield of enantioselective alkylation reaction can be increased by using Dy(OTf)₃ as a catalyst. In contrast to ytterbium and lanthanum, dysprosium is the most effective catalyst.

• Additional dysprosium-catalyzed reactions:

Dysprosium can be used in other reactions that require lanthanide catalysts, and it generally has the best catalytic effect. In addition, since Dy(OTf)₃ is stable, it can be used in protic media and ionic liquids.

References

1. Trost, B. M (1991). 'In Comprehensive Organic Synthesis'. Pergamon. 3,293-339.
2. Meija, Juris. (2016). 'Atomic weights of the elements 2013 (IUPAC Technical Report)'. Pure and Applied Chemistry. 88 (3): 265-291.
3. Gesine K (2012). 'Dysprosium(III) catalysis in organic synthesis'. Tetrahedron. 68, 2015-2026.