Catalytic cycle for

Figure C2.7.4. Catalytic cycle for hydrogenation of methyl-(Z)-a-acetamidocinnamate tire rate constants were measured at 298 K S is solvent [8],...

Scheme 2.6. Catalytic cycle for a Lewis-acid catalysed Diels-Alder reaction.

The most useful reaction of Pd is a catalytic reaction, which can be carried out with only a small amount of expensive Pd compounds. The catalytic cycle for the Pd(0) catalyst, which is understood by the combination of the aforementioned reactions, is possible by reductive elimination to generate Pd(0), The Pd(0) thus generated undergoes oxidative addition and starts another catalytic cycle. A Pd(0) catalytic species is also regenerated by /3-elimination to form Pd—H which is followed by the insertion of the alkene to start the new catalytic cycle. These relationships can be expressed as shown. 

Donation of a proton to the reactant often forms a carbenium ion or an oxonium ion, which then reacts ia the catalytic cycle. For example, a catalytic cycle suggested for the conversion of phenol and acetone iato bisphenol A, which is an important monomer used to manufacture epoxy resias and polycarbonates, ia an aqueous mineral acid solution is shown ia Figure 1 (10). 

Fig. 1. Catalytic cycle for synthesis of bisphenol A from phenol and acetone in the presence of a dissociated mineral acid (10).

Fig. 18. Schematic representation of the catalytic cycle for ammoxidation of propylene and related reactions. and M2 represent the two metals in a...

Scheme 15.1 Catalytic cycle for the conversion of a diselenide to a selenenic acid...

The palladium-catalyzed hnear telomerization of 1,3-bntklienes provides a useful method for thepreparation of functionalized alkenes. A proposed catalytic cycle for the paliadinm-catalyzed... 

Scheme 8. Catalytic cycle for the BINAP-Rh(i)-catalyzed asymmetric isomerization of allylic amines.

Although analogous to the direct coupling reaction, the catalytic cycle for the carbonylative coupling reaction is distinguished by an insertion of carbon monoxide into the C-Pd bond of complex A (see A—>B, Scheme 31). The transmetalation step-then gives trans complex C which isomerizes to the cis complex D. The ketone product E is revealed after reductive elimination. 

Scheme 9. The two catalytic cycles for the Sharpless AD with NMO as a cooxidant.

With some systems, the hydroperoxide is reduced to hydroperoxy radical by the metal ion in its higher oxidation state (Scheme 3.39). Thus, it is possible to set up a catalytic cycle for hydroperoxide decomposition. 

The general catalytic cycle for the coupling of aryl-alkenyl halides with alkenes is shown in Fig. 9.6. The first step in this catalytic cycle is the oxidative addition of aryl-alkenyl halides to Pd(0). The activity of the aryl-alkenyl halides still follows the order RI > ROTf > RBr > RC1. The olefin coordinates to the Pd(II) species. The coordinated olefin inserts into Pd—R bond in a syn fashion, p-Hydrogen elimination can occur only after an internal rotation around the former double bond, as it requires at least one /I-hydrogen to be oriented syn perpendicular with respect to the halopalladium residue. The subsequent syn elimination yields an alkene and a hydridopalladium halide. This process is, however, reversible, and therefore, the thermodynamically more stable (E)-alkene is generally obtained. Reductive elimination of HX from the hydridopalladium halide in the presence of a base regenerates the catalytically active Pd(0), which can reenter the catalytic cycle. The oxidative addition has frequently assumed to be the rate-determining step. 

OUTLINE OF THE CATALYTIC CYCLE FOR THE HECK COUPLING REACTION... 

Scheme 1. Catalytic Cycle for the TEMPO/NaOCl Catalyzed Oxidation...

Scheme 12 Proposed catalytic cycle for Casey s hydrogenation...

The proposed catalytic cycle for the dehydrogenation of alcohols to ketones is shown in Scheme 15. The initial reaction of 17 with H2O affords the hydride complex a and C02- Dehydrogenation of a by acetone gives the active species b and 2-propanol. The subsequent reaction of b with the alcohol yields the corresponding ketone and regenerates a to complete the catalytic cycle. 

Scheme 15 Proposed catalytic cycle for dehydrogenation of alcohols to ketones...

Scheme 34 Proposed catalytic cycle for the C-C bond formation...

Scheme 38 Catalytic cycle for the hydrogen-mediated enyne cyclization...

Fig. 36 Catalytic cycle for the Br0nsted-base catalyzed addition of phenols, hydrazoic acid, or 2-cyanopyirol to ketenes...

Scheme 31 Catalytic cycle for the iron-catalyzed carbonylation proposed by Seller et al. [94]...

Figure 9.6. Schematic representation of the catalytic cycle for the hydrodesulfurization of a sulfur-containing hydrocarbon (ethane thiol) by a sulfur vacancy on M0S2 The C2H5SH molecule adsorbs with its sulfur atom towards...

Figure 10.15. Catalytic cycle for the SCR process over acidic V -OH sites and redox V=0 sites. [Adapted from N.-Y. Topsoe, Science 26S (1994) 1217.]...

Since this scheme regenerates the original coordinatively unsaturated Ti+2 centers upon desorption of the aromatic, it could, in principle, represent a catalytic cycle for heterogeneous alkyne cyclization. The present study reports a test of that h3T>othesis—the feasibility of catal5hic cyclotrimerization—on a reduced Ti02 surface in UHV. 

Scheme 6.1 General catalytic cycle for cross-coupUng reactions...

Scheme 6.5 Catalytic cycle for the Mizoroki-Heck reaction...

Scheme 1-11 Catalytic Cycle for Metal-Phosphine Complexes...

Scheme 1-12 Catalytic Cycle for Phosphine-Free Rh(l) Complexes...

RCH2CH2Bcat HBeat Scheme 1-13 Catalytic Cycle for Cp2Ti... 

Scheme 1-14 Catalytic Cycle for Lantanide and Group 5 Metals...

R =H, R =alkyl for terminal alkynes R =alkyl, R =H for terminal alkenes Catalytic Cycle for Addition to Alkenes and Alkynes... 

Scheme 4-3 Catalytic cycle for the organolanthanide-catalyzed IH of aminoalkenes...

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