Catalysts second-/third-generation

A domino Diels-Alder reaction (the term was chosen from the well-known game) is a one-pot process involving two or more Diels-Alder reactions carried out under the same reaction conditions without adding additional reagents or catalyst such that the second, third, etc., cycloaddition is the consequence of the functionality generated in the previous reaction. A historical example is illustrated in Equation 1.28 [60]. This type of transformation is sometimes named tandem or cascade, but these terms seem less appropriate for describing a time-resolved transformation. 

Fig. 3.28 ROMP initiators, first, second and third generation Grubbs catalysts (complexes 71, 72, and 73, respectively) 74a-c 3-phenyl-indenylidene replaces the benzylidene carbene...

Carbene ligands can replace phosphines dne to similar electronic properties. The development of NHC design concepts featnring different substituents and backbones eventually culminated in the most prominent derivative, the SIMes (SDVtes = A, A -bis[2,4,6-(trimethyl)phenyl]imidazolidin-2-ylidene) ligand that is nsed in the second and later also third generation catalysts (complexes 72, 73, 74b and 74c in Fig. 3.28) [105, 109, 114,116],... 

The so-called second generation ionic hquids were prepared from organic cations and AlCl anions [170]. Since AICI3 was present in these liquids, they were used as catalysts in Lewis acid catalyzed reactions. Also many of the third generation ionic liquids have been used as solvents for catalytic reactions [171-174], However, it is also known that third generation ionic liquids are capable of catalyzing reactions, either in substoichiometric amounts or as reaction medium. This will be discussed in this section. 

These palladium-functionalized dendrimers show selectivity for the linear reaction product. A drop in activity was found when the catalysts were reused (1-decene as substrate/G(4)Pd(PPh3)2 dendrimer as catalyst 92, 75, 73, and 45% yield for the first, second, third, and fourth, respectively). The (dba)Pd-PPh2-PAMAM-Si02 dendrimers of generations 0—4 showed activity for the oxidation of terminal alkenes under mild conditions. The catalytic activity was found to be dependent on... 

Fig. 3 Olefin metathesis catalysts Schrock tungsten (Cl) and molybdenum (C2) alkylidene complexes, Grubbs first- (C3) and second-generation (C4) catalysts, Hoveyda-Grubbs second-generation catalyst (C5), and Grubbs third-generation catalyst (C6)...

The DHC-8 and HC-24 catalysts in Figure 4.12 are second-generation, state-of-the-art catalysts for maximum diesel and maximum naphtha, respectively. In 2000-2001, UOP introduced a third generation of hydrocracking catalysts that further improve the efficiency of the hydrocracking process (15). HC-110 is a third-generation maximum-diesel catalyst that provides up to 3 vol-% higher distillate yield than DHC-8 at the same activity. Another distillate catalyst, HC-... 

Figure 17.1 shows a block diagram of the notable process simplification on moving from second- (low yield slurry process) to third-generation catalysts (high yield slurry... 

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