Silica-supported Phosphine Palladium(0) Complex Catalysed Cross-coupling of Organic Halides with Organotin and Organomagnesium Reagents

Article abstract of DOI:10.1039/a707180i

Silica-supported phosphine palladium(0) complex is an efficient catalyst for the cross-coupling of organic halides, except for aliphatic halides, with organotin and organomagnesium reagents; the polymeric catalyst is stable and can be easily separated from a reaction mixture and reused.

Full text of DOI:10.1039/a707180i

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264 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 264±265$
Silica-supported Phosphine Palladium(0) Complex
Catalysed Cross-coupling of Organic Halides with
Organotin and Organomagnesium Reagents$
Ming-Zhong Cai,a Cai-Sheng Songb and Xian Huang*a
aDepartment of Chemistry, Hangzhou University, Hangzhou 310028, P.R. China
bDepartment of Chemistry, Jiangxi Normal University, Nanchang 330027, P.R. China
Silica-supported phosphine palladium(0) complex is an efficient catalyst for the cross-coupling of organic halides, except
for aliphatic halides, with organotin and organomagnesium reagents; the polymeric catalyst is stable and can be easily
separated from a reaction mixture and reused.
The palladium-catalysed cross-coupling reaction has consti-
tuted an important method for organic synthesis, and a
wide variety of organic electrophiles and organometallic
reagents can be used.1±4 For example, the cross-coupling of
organic halides such as acid chlorides,5 aryl halides6 and
vinyl halides7 with organotin compounds has been reported
to be readily achieved in the presence of a palladium com-
plex in high yields. In most cases, homogeneous catalysts
are used, but it is dicult to recover them from products.
The development of useful reactions catalysed by soluble
transition metals has led to interest in evolving `insolubi-
lized' versions of these catalysts for ease of recovery and
work-up.8 Hybrid catalysts combining the attributes of
conventional homogeneous catalysts with the experimental
simplicity of heterogeneous catalysts have been proven to
be fruitful subjects for research by both academic and
industrial chemists.9 We have studied the phenylation of
acid chlorides and aryl iodides by sodium tetraphenylborate,
using a silica-supported phosphine palladium(0) complex
(`Si'±P±Pd0).10 However, to our knowledge, there has been
no speci®c report regarding polymer-bound palladium
catalyst for the cross-coupling of organic halides with
organotin and organomagnesium reagents. To extend the
application of polymeric catalysts (`Si'±P±Pd0) to other
organic reactions, we presently wish to report the char-
with tetramethyltin. However, the reactivity of aliphatic acid
chlorides was poor and only trace products were obtained.
The cross-coupling of methyl 4-iodobenzoate with tetra-
methyltin also proceeded smoothly at 65 8C in the presence
of `Si'±P±Pd0 without CuI, and methyl 4-methylbenzoate
was obtained after 20 h in 88% yield. However, the reac-
tivity of methyl 4-bromobenzoate is obviously lower than
that of the corresponding iodide under the same conditions
(Table 1).
The cross-coupling reaction between aryl halides and
phenylmagnesium bromide readily took place in tetrahydro-
furan (THF) and in the presence of a catalytic amount of
`Si'±P±Pd0; the results are also summarized in Table 1. Aryl
iodides coupled with phenylmagnesium bromide at room
temperature for 20 h to give the cross-coupled products
almost exclusively, in high yields, whereas 4-methylbromo-
benzene reacted with phenylmagnesium bromide in re¯uxing
THF to give 4-methyldiphenyl as the main product together
with a considerable amount of homocoupled diphenyl.
In conclusion, the silica-supported phosphine palladium(0)
complex described here can eciently catalyse the cross-
coupling reaction of organic halides with organotin and
organomagnesium reagents; this polymeric palladium
catalyst can be reused without noticeable loss of activity.
The method presented for preparing ketones and biaryls has
the advantages of readily available starting materials, simple
and practical procedures, mild reaction conditions and good
yields.
acteristic features of
a polymeric palladium(0) catalyst
(`Si'±P±Pd0) for the cross-coupling reactions of organic
halides with organotin and organomagnesium reagents
(Scheme 1).
Experimental
Mps were uncorrected. IR spectra were obtained on a Shimadzu
IR-435 instrument. The 1H NMR spectra were obtained on a JEOL
FX-90Q (90 MHz) instrument with Me4Si as an internal standard in
CDCl3 as solvent. All solvents were dried and distilled before use.
Preparation of Poly-ꢀ-(diphenylphosphino)propylsiloxane(`Si'±P).
ÐA mixture of fumed silica (6.0 g) and ꢀ-chloropropyltriethoxy-
silane (5.0 g) in toluene (140 ml) was stirred at 120 8C for 24 h.
Distilled water (20 ml) and 10% hydrochloric acid (0.2 ml) were
added and the mixture was boiled under re¯ux for another 48 h.
After being cooled to room temperature, the mixture was ®ltered,
washed with distilled water (4 Â 50 ml) and dried under vacuum.
The resulting white powder was stirred with 1,1,1,3,3,3-hexamethyl-
disilazane (10 ml) in toluene (80 ml) at 100 8C for 48 h. The mixture
was allowed to cool and then ®ltered, washed with toluene
(3Â 20 ml) and acetone (3 Â20 ml) and dried under vacuum to give
7.0 g of poly-ꢀ-chloropropylsiloxane ('Si'±Cl). The chlorine content
was 7.24 wt%.
Scheme 1 R1 ˆ Ar, ArCO; X ˆ Cl, Br, I; R2 ˆ Me, Ph;
M ˆ SnMe3, MgBr
Treatment of benzoyl chloride (2 mmol) with tetra-
methyltin (2,2 mmol) in hexamethylphosphoric triamide
(HMPA, 1 ml) at 65 8C for 20 h in the presence of
a catalytic amount of `Si'±P±Pd0 (0.02 mmol, 1 mol%)
a€orded acetophenone in 85% yield. The catalytic activity
of the recovered catalyst was tested for the cross-coupling of
benzoyl chloride with tetramethyltin for two recycles and it
was found that the yield of acetophenone decreased by 2
and 5% in each recycle, respectively. The cross-coupling
reaction can tolerate a number of other functional groups
on the acid chlorides, e.g. Cl, NO2, CO2CH3 substituents
are not a€ected. Typical results are summarized in Table 1.
As is evident, a variety of substituted acetophenones can
successfully be prepared by treating aromatic acid chlorides
To
(0.15 mol dm
a
100 ml THF solution of lithiodiphenylphosphine
)
3
was added `Si'±Cl(6.0 g), and the mixture was
boiled under re¯ux under nitrogen for 30 h. After being cooled to
room temperature, 2-chloro-2-methylpropane (2 ml) was added
and the mixture was stirred at room temperature for 2 h. The mix-
ture was ®ltered, washed with ethanol (3 Â 30 ml) and distilled
water (5Â40 ml) and dried under vacuum to give 6.5 g of poly-g-
(diphenylphosphino)propylsiloxane (`Si'±P). The phosphine content
was 4.37 wt%.
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).

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J. CHEM. RESEARCH (S), 1998 265
Table 1 Cross-coupling of organic halides with organotin and organomagnesium reagentsa
Organic halide
Sn/Mg reagent
Conditions
Product (% yield)b
PhCOCl
SnMe4
SnMe4
SnMe4
SnMe4
SnMe4
SnMe4
SnMe4
PhMgBr
PhMgBr
PhMgBr
PhMgBr
HMPA, 65 8C
HMPA, 65 8C
HMPA, 65 8C
HMPA, 65 8C
HMPA, 65 8C
HMPA, 65 8C
HMPA, 65 8C
THF, 30 8C
PhCOCH3(85)
4-ClC6H4COCl
4-CH3OC6H4COCl
2-ClC6H4COCl
4-NO2C6H4COCl
4-CH3OCOC6H4I
4-CH3OCOC6H4Br
PhI
4-CH3OC6H4I
PhBr
4-CH3C6H4Br
4-ClC6H4COCH3(81)
4-CH3OC6COCH3(80)
2-ClC6H4COCH3(76)
4-NO2C6H4COCH3(83)
4-CH3C6H4CO2CH3(88)
4-CH3C6H4CO2CH3(70)
Ph2(95)
4-CH3OC6H4C6H5(90)
Ph2(85)
4-CH3C6H4Ph(79)
THF, 30 8C
THF, 65 8C
THF, 65 8C
aCoupling reactions of organic halides with organotin reagent were carried out at 65 8C with
2 mmol of acid chloride or aryl halide, 2.2 mmol of tetramethyltin and 0.02 mmol of palladium
catalyst in 1 ml of HMPA for 20 h; coupling reactions of aryl halides with organomagnesium
reagent were carried out at 30 or 65 8C with 1mmol of aryl halide, 1.5 mmol of
phenylmagnesium bromide and 0.01 mmol of palladium catalyst in 5 ml THF for 20 h. bYields are
of isolated, pure product and based on the organic halides.
Preparation of `Si'±P±Pd 0.ÐTo a solution of PdCl2 (0.15 g) in
water (2Â 20 ml), dried over anhydrous magnesium sulfate and
concentrated under reduced pressure. The residue was puri®ed by
preparative TLC on silica gel (light petroleum) to give diphenyl
acetone (40 ml) was added `Si'±P (2.05 g). The mixture was re¯uxed
under nitrogen for 48 h. The yellow solid produced was ®ltered o€,
washed with acetone (3 Â 30 ml), then stirred with hydrazine hydrate
(1.50 g, 30 mmol) and EtOH (20 ml) at 30 8C under nitrogen for
3 h. The resulting product was ®ltered o€, washed with EtOH
(4Â 30 ml) and Et2O (2Â 30 ml and dried under vacuum to give
1.86 g of the dark-green polymeric palladium(0) complex. The palla-
dium content was 3.20 wt% and the phosphine content was 3.45
wt%.
(0.146 g, 95%).
Diphenyl: Mp 69±70 8C (lit.17 70 8C); ꢁmax (KBr)/cm
1600, 1480, 730, 695; dH (CDCl3) 6.95±7.55 (10 H, m).
1
3040,
4-Methoxydiphenyl: Mp 87±88 8C (lit.15 90±91 8C); ꢁmax (KBr)/
cm 1, 3030, 1600, 1485, 1440, 1250, 1035, 830, 760; dH (CDCl3 3.72
(3 H, s), 6.81 (2 H, d, J 9.0 Hz), 7.05±7.70 (7 H, m).
1
4-Methyldiphenyl: Mp 46±47 8C (lit.16 47.5 8C); ꢁmax (KBr)/cm
Typical Procedure for the Cross-coupling of Organic Halides with
Tetramethyltin.ÐA mixture of SnMe4 (0.393 g, 2.2 mmol), benzoyl
chloride (0.282 g, 2 mmol) and `Si'±P±Pd0 (0.070 g, 0.02 mmol) in
HMPA (1 ml) was stirred under nitrogen at 65 8C for 20 h. The
reaction mixture was cooled, dissolved in diethyl ether (50 ml).
The `Si'±P±Pd0 was separated from the mixture by ®ltration,
washed with diethyl ether (3 Â 30 ml), dried in vacuo and reused
in the next run. The ethereal solution was washed with distilled
water (5Â 30 ml, dried over anhydrous magnesium sulfate and con-
centrated under reduced pressure. The residue was puri®ed by pre-
parative TLC on silica gel (light petroleum±ethyl acetate ˆ 7:1) to
a€ord acetophenone (0.204 g, 85%).
3050, 1485, 820, 750, 690; dH (CDCl3) 2.32 (3 H, s), 6.95±7.62
(9 H, m).
This work was supported by the Natural Science
Foundation of Jiangxi Province in China.
Received, 6th October 1997; Accepted, 20th January 1998
Paper E/7/07180I
1
Acetophenone.5 ꢁmax (®lm)/cm 3050, 2940, 1680, 1600, 1450,
References
1360, 760, 690; dH (CDCl3) 2.53 (3 H, s), 7.22±7.60 (3 H, m), 7.75±
7.98 (2 H, m).
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1
4'-Chloroacetophenone:5 ꢁmax (®lm)/cm 3060, 2920, 1680, 1590,
1490, 1360, 820; dH (CDCl3) 2.80 (3 H, s), 7.73 (2 H, d, J 9.0 Hz),
8.20 (2 H, d, J 9.0 Hz).
3040, 2920, 1675,
1
4'-Methoxyacetophenone:5 ꢁmax (®lm)/cm
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7.05 (2 H, d, J 9.0 Hz), 8.04 (2 H, d, J 9.0 Hz).
1
2'-Chloroacetophenone:11 ꢁmax (®lm)/cm 3050, 2920, 1690, 1590,
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1
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Typical Procedure for the Cross-coupling of Aryl Halides with
Phenylmagnesium.ÐA mixture of phenylmagnesium bromide
(1.5 mmol), iodobenzene (1 mmol) and `Si'±P±Pd0 (0.01 mmol) in
THF (5 ml) was stirred under nitrogen at 30 8C for 20 h. Then
a saturated aqueous NH4Cl solution (30 ml) was added and the
mixture was stirred at 30 8C for 10 min, and extracted with diethyl
ether (2Â30 ml. The ethereal solution was washed with distilled
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