PALLADIUM GRAPHITE 1
Palladium Graphite 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
Pd Gr
elimination, yield the corresponding arylated or allylated com-
pounds.2 Aryl bromides should not be used as they are not as
[59873-73-3] Pd (MW 106.42)
reactive under these reaction conditions. By using a stoichiomet-
InChI = 1/Pd
ric amount of a tertiary amine to trap the HI, the reaction can be
InChIKey = KDLHZDBZIXYQEI-UHFFFAOYAH
carried out with a catalytic amount of palladium. When mono-
substituted alkenes are used, high stereospecificity is achieved,
(hydrogenation catalyst for aromatic nitro compounds, alkenes,
thereby affording substituted (E)-alkenes (eqs 5 and 6). The yields
and alkynes;1 catalyzes arylation and vinylation of activated
are comparable with those reported using other palladium cata-
double bonds2,3)
lysts such as Palladium(II) Acetate.
Physical Data: 31 33% Pd by weight.
Form Supplied in: not commercially available.
PhI, Pd Gr
H H Ph H
EDA
Preparative Method: by reduction of Palladium(II) Chloride
(5)
ć%
Bu3N
by Potassium Graphite in 1,2-dimethoxyethane at 100 C.1
H Ph H Ph
92%
Handling, Storage, and Precautions: no special handling or
92% E
storage necessary; the catalyst is stable in air and can be stored
for a long time without loss of activity.
I
( )4
H H
Pd Gr
CO2Et
(6)
( )4
Hydrogenation Catalyst. Palladium graphite is an effective
Bu3N
H CO2Et
58% 80% EE
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
Substitution reactions of allylic esters are also catalyzed
to the more commonly used Palladium on Carbon catalyst.
by palladium graphite.3 The reaction between allyl acetate and
Sodium Benzenesulfinate in the presence of catalytic amounts of
Pd Gr
(1)
O2NH2N
Pd Gr and Triphenylphosphine afforded the allyl phenyl sulfone
MeOH
100% in quantitative yield (eq 7). In fact, the catalyst can be recovered
and after ten runs the yield was 93%, showing that the catalyst
Pd Gr
retains its activity.
(2)
MeOH
100%
PhSO2Na
O
Pd Gr, PPh3
SO2Ph
The catalyst has also been found to be effective in the stereo-
(7)
100%
O
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
1. Savoia, D.; Trombini, C.; Umani-Ronchi, A.; Verardo, G., J. Chem. Soc.,
fact, higher specificity is achieved with palladium graphite com- Chem. Commun. 1981, 540.
pared to palladium on carbon in the presence of ethylenediamine
2. Savoia, D.; Trombini, C.; Umani-Ronchi, A.; Verardo, G., J. Chem. Soc.,
although the rate of hydrogenation is slower. Chem. Commun. 1981, 541.
3. Boldrini, G. P.; Savoia, D.; Tagliavini, E.; Trombini, C.; Umani-Ronchi,
Pd Gr
H
A., J. Organomet. Chem. 1984, 268, 97.
7
EDA
H (3)
MeOH
7
H H
Ellen M. Leahy
95%
Affymax Research Institute, Palo Alto, CA, USA
Pd Gr
Ph
EDA
(4)
Ph Ph
MeOH
Ph
97%
94% Z
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