PALLADIUM–GRAPHITE

1

Palladium–Graphite

Pd–Gr

[59873-73-3]

Pd

(MW 106.42)

InChI = 1/Pd
InChIKey = KDLHZDBZIXYQEI-UHFFFAOYAH

(hydrogenation catalyst for aromatic nitro compounds, alkenes,
and alkynes;

1

catalyzes arylation and vinylation of activated

double bonds

2

,

3

)

Physical Data:

31–33% Pd by weight.

Form Supplied in:

not commercially available.

Preparative Method:

by reduction of Palladium(II) Chloride

by Potassium–Graphite in 1,2-dimethoxyethane at 100

◦

C.

1

Handling, Storage, and Precautions:

no special handling or

storage necessary; the catalyst is stable in air and can be stored
for a long time without loss of activity.

Hydrogenation Catalyst. Palladium–graphite is an effective

catalyst for hydrogenation of aromatic nitro compounds to ani-
lines (eq 1) and alkenes to alkanes (eq 2).

1

The results of these

investigations indicated that palladium–graphite is an alternative
to the more commonly used Palladium on Carbon catalyst.

O

2

N

H

2

N

Pd–Gr

(1)

MeOH

100%

Pd–Gr

(2)

MeOH

100%

The catalyst has also been found to be effective in the stereo-

specific semihydrogenation of mono- and disubstituted alkynes
to (Z)-alkenes (eqs 3 and 4).

1

Addition of 1,2-Diaminoethane

(EDA) is required for this stereospecificity to be achieved. Full
hydrogenation is almost completely suppressed and results are
comparable to those obtained by Lindlar or P-2 nickel catalysts. In
fact, higher specificity is achieved with palladium–graphite com-
pared to palladium on carbon in the presence of ethylenediamine
although the rate of hydrogenation is slower.

H

H

H

H

Pd–Gr

EDA

7

7

(3)

MeOH

95%

Ph

Ph

Pd–Gr

EDA

Ph

Ph

(4)

94% Z

MeOH

97%

Arylation and Vinylation of Activated Double Bonds.

Palladium–graphite undergoes oxidative addition into the carbon–
halogen bond of aryl and vinyl iodides, which, after reductive
elimination, yield the corresponding arylated or allylated com-
pounds.

2

Aryl bromides should not be used as they are not as

reactive under these reaction conditions. By using a stoichiomet-
ric amount of a tertiary amine to trap the HI, the reaction can be
carried out with a catalytic amount of palladium. When mono-
substituted alkenes are used, high stereospecificity is achieved,
thereby affording substituted (E)-alkenes (eqs 5 and 6). The yields
are comparable with those reported using other palladium cata-
lysts such as Palladium(II) Acetate.

H

H

H

Ph

H

Ph

H

Ph

PhI, Pd–Gr

EDA

(5)

92% E

Bu

3

N

92%

H

H

H

CO

2

Et

80% EE

I

Pd–Gr

( )

4

CO

2

Et (6)

( )

4

Bu

3

N

58%

Substitution reactions of allylic esters are also catalyzed

by palladium–graphite.

3

The reaction between allyl acetate and

Sodium Benzenesulfinate in the presence of catalytic amounts of
Pd–Gr and Triphenylphosphine afforded the allyl phenyl sulfone
in quantitative yield (eq 7). In fact, the catalyst can be recovered
and after ten runs the yield was 93%, showing that the catalyst
retains its activity.

PhSO

2

Na

Pd–Gr, PPh

3

O

O

SO

2

Ph

(7)

100%

1.

Savoia, D.; Trombini, C.; Umani-Ronchi, A.; Verardo, G., J. Chem. Soc.,
Chem. Commun. 1981

, 540.

2.

Savoia, D.; Trombini, C.; Umani-Ronchi, A.; Verardo, G., J. Chem. Soc.,
Chem. Commun. 1981

, 541.

3.

Boldrini, G. P.; Savoia, D.; Tagliavini, E.; Trombini, C.; Umani-Ronchi,
A., J. Organomet. Chem. 1984, 268, 97.

Ellen M. Leahy

Affymax Research Institute, Palo Alto, CA, USA

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