Article
Organometallics, Vol. 28, No. 16, 2009 4699
(2 mL), and 2,6-lutidine (78 mL, 0.68 mmol) and [Cu(Me-
CN)4](PF6) were added. The resulting mixture was stirred at
room temperature for 24 h. Next, Et2O (∼2 mL) was added,
resulting in a yellow precipitate. This precipitate was collected,
washed with Et2O (2 ꢀ 2 mL), and dried in vacuo.
EtOH (2ꢀ), acetone (2ꢀ), CH2Cl2 (2ꢀ), and pentane (2ꢀ),
and subsequently dried under vacuum. Light yellow powder.
IR (DRIFT, difference): νcarbamate 1641 and 1562 cm-1, νCNO
2276 cm-1 (trough), νSiO-H 3740 cm-1 (trough). Anal. Found:
C 6.45, H 1.81, N, 2.12, Pd 0.26.
1-Benzyl-4-[2,6-bis[(dimethylamino)methyl]-1-palladium(II)
bromide-benzene]-1H-1,2,3-triazole, 9. Brown powder, 82%
yield. 1H NMR (400 MHz, DMSO-d6): δ 2.71 (s, 12H, N(CH3)2,
4.10 (s, 4H, CH2N), 5.62 (s, 2H, CH2Ph), 7.31-7.39 (m, 7H, ArH),
8.53 (s, 1H, H-triazole). 13C NMR (100 MHz, DMSO-d6): δ 52.55,
53.87, 73.60, 117.88, 121.11, 128.20, 128.57, 128.91, 129.51, 136.58,
145.56, 146.51, 148.03. MALDI-TOF (9-nitroanthracene, MeCN)
(m/z): 542.14 (calcd M - Br 454.12). Anal. Calcd for C21H26-
Synthesis of TMS-capped-3-[4-(N-carbamato)-2,6-bis[(dimeth-
ylamino)methyl]-1-platinum(II) chloride-benzene]propyl-1-silica, 8.
4-(tert-Butyldimethylsiloxy)-2,6-bis[(dimethylamino)methyl]-
1-platinum(II) chloride-benzene (0.054 g, 0.1 mmol) was dis-
solved in a CH2Cl2/MeOH mixture (1:1, 10 mL) and stirred
over an ion-exchange resin (DOWEX 50WX8) for 24 h.
The resulting solution was filtered and solvent was removed.
The resulting solid was dissolved in CH2Cl2 (20 mL) with NEt3
(3 mL, large excess), 4-dimethylaminopyridine (0.005 g, cat.,
0.04 mmol), and TMS-capped-3-isocyanatopropyl-1-silica
(1 g) and was stirred at reflux for 24 h. The mixture was filtered
hot, then washed with EtOH (2ꢀ), acetone (2ꢀ), CH2Cl2 (2ꢀ),
and pentane (2ꢀ), and subsequently dried under vacuum.
Yellow powder. IR (DRIFT, difference): νcarbamate 1648 and
1548 cm-1, νCNO 2276 cm-1 (trough), νSiO-H 3740 cm-1
(trough). Anal. Found: C 11.62, H 2.53, N, 2.17, Pt 0.79.
Standard Conditions for Double Michael Addition. Catalyst
(0.0025 mmol active cat.), cyanoacetic acid ethyl ester (0.03 g,
0.25 mmol, ethyl cyanoacetate), 3-buten-2-one (0.056 g, 0.79 mmol,
ClN5Pt 4H2O: C, 41.56; H, 5.65; N, 11.54. Found: C, 41.80; H,
3
5.12; N, 11.35. IR: νtriazole 1450-1430 cm-1
.
1-Benzyl-4-[2,6-bis[(dimethylamino)methyl]-1-platinum(II)
bromide-benzene]-1H-1,2,3-triazole, 10. Off-yellow powder,
1
96% yield. H NMR (400 MHz, DMSO-d6): δ 2.92 (s, 12H,
N(CH3)2, 4.07 (s, 4H, CH2N), 5.58 (s, 2H, CH2Ph), 7.25 (s, 2H,
ArH), 7.30-7.37 (m, 5H, ArH), 8.43 (s, 1H, H-triazole). 13C
NMR (100 MHz, DMSO-d6): δ 53.63, 55.60, 77.27, 116.89,
120.84, 126.12, 128.53, 128.80, 129.46, 138.82, 144.84, 146.70,
148.99. MALDI-TOF (9-nitroanthracene, MeCN) (m/z): 578.15
(calcd 578.15), 542.17 (calcd M - Cl 542.64). Anal. Calcd for
C21H26ClN5Pt: C, 43.56; H, 4.53; N, 12.10. Found: C, 43.67; H,
€
methyl vinyl ketone), and diisopropylethylamine (Hunigs base,
4.50; N, 12.06. IR (ATR): νtriazole 1450-1430 cm-1
.
0.005 g, 0.025 mmol) were placed in CH2Cl2 (1 mL, dry
degassed). The mixture was stirred at room temperature until
the reaction was complete. Aliquots of 10 μL were taken at
regular time intervals (varied depending on whether homo or
hetero cat.). All volatiles were then removed under a steady
stream of nitrogen, and the remaining oil was dissolved in
CDCl3 for 1H NMR analysis.
Standard Conditions for Allylic Stannylation. Catalyst (0.0026
mmol active cat.), hexamethyldistannane (0.082 g, 0.25 mmol),
and 3-chloro-1-propenylbenzene (0.38 g, 0.25 mmol, cinnamyl
chloride) were placed in dry, degassed THF (1 mL). The mix-
ture was stirred at room temperature until the reaction
was complete. Aliquots of 10 μL were taken at regular time
intervals (varied depending on whether homo or hetero cat.). All
volatiles were then removed under a steady stream of nitrogen, and
the remaining oil was dissolved in CDCl3 for 1H NMR analysis.
Recycling. Catalytic mixtures were poured over a glass frit
(#4) and subsequently washed with the solvent used during the
catalytic experiment (CH2Cl2 for Michael, THF for both stan-
nylation and allylic alkylation). This method led to loss of some
catalytic material, which could not be removed from the frit.
Another technique is to centrifuge the reaction mixture to
separate the insoluble catalytic material.
Sequential Experiments: Standard Conditions for Allylic Alky-
lation. Catalyst (0.0026 mmol active cat., a PCP-Pd complex
tethered to silica previously synthesized in our group19) and
4-nitrobenzaldehyde (0.038 g, 0.25 mmol) were placed in the
dry, degassed filtrate solution from the allylic stannylation
reaction. Material 4 was removed prior to addition of the
PCP-Pd catalyst and nitrobenzaldehyde using the same techni-
que used for catalyst recycling mentioned above (the stannyla-
tion reaction mixture was placed in a centrifugation vessel, and
the catalyst and substrates were separated from each other,
followed by filtration). The mixture was stirred at room tem-
perature for 24 h. All volatiles were then removed under a steady
stream of nitrogen, and the remaining oil was dissolved in
CDCl3 for 1H NMR analysis.
Synthesis of 3-Aminopropyl-1-silica. Silica (5 g, BASF bv
nederland, C500-383) and 3-aminopropyl-1-(triethoxy)silane
(5 mL, 0.021 mol) were placed in dry toluene (100 mL) and
heated at reflux for 24 h. The mixture was filtered hot,
then washed with toluene (2ꢀ), boiling EtOH (2ꢀ), acetone
(2ꢀ), CH2Cl2 (2ꢀ), and pentane (2ꢀ), and subsequently dried
under vacuum. White powder. IR (DRIFT, difference): νSiO-H
3740 cm-1 (trough).
Synthesis of TMS-capped-3-aminopropyl-1-silica. 3-Amino-
propyl-1-silica (5 g) was placed in dry hexanes (50 mL) with
hexamethyldisilazane (5 mL, 3.87 g, 0.024 mol), and the mixture
was heated at reflux for 24 h. The mixture was filtered hot, then
washed with pentane (2ꢀ), boiling EtOH (2ꢀ), CH2Cl2 (2ꢀ),
and pentane (2ꢀ), and subsequently dried under vacuum. White
powder. IR (DRIFT, difference): νSiO-H 3740 cm-1 (trough).
Synthesis of TMS-capped-3-isocyanatopropyl-1-silica, 2. TMS-
capped-3-aminopropyl-1-silica (5 g) was placed in a Schlenk with
toluene (30 mL, dry degassed). Triphosgene (2.03 g, 6.8 mmol)
was added, and the resulting mixturewas heated atreflux for 24 h.
The mixture was filtered hot, then washed with toluene (2ꢀ),
acetone (2ꢀ), CH2Cl2 (2ꢀ), and pentane (2ꢀ), and subsequently
dried under vacuum. White powder. IR (DRIFT, difference):
νCNO 2276 cm-1, νSiO-H 3740 cm-1 (trough). Anal. Found: C
7.47, H 2.20, N, 0.77.
Synthesis of TMS-capped-3-(benzylcarbamato)propyl-1-sili-
ca, 6. TMS-capped-3-isocyanatopropyl-1-silica (1 g) was placed
in dry toluene (5 mL) with benzyl alcohol (1 mL, 9.7 mmol) and
stirredat reflux for 24 h. The mixturewas filtered hot, then washed
with toluene (2ꢀ), boiling EtOH (2ꢀ), acetone (2ꢀ), CH2Cl2
(2ꢀ), and pentane (2ꢀ), and subsequently dried under vacuum.
White powder. IR (DRIFT, difference): νcarbamate 1700 and
1530 cm-1, νCNO 2276 cm-1 (trough), νSiO-H 3740 cm-1 (trough).
Synthesis of TMS-capped-3-[4-(N-carbamato)-2,6-bis[(dime-
thylamino)methyl]-1-palladium(II) bromide-benzene]propyl-1-si-
lica, 7. 4-(tert-Butyldimethylsiloxy)-2,6-bis[(dimethylamino)-
methyl]-1-palladium(II) bromide-benzene (0.05 g, 0.11 mmol)
was dissolved in a CH2Cl2/MeOH mixture (1:1, 10 mL) and
stirred over an ion-exchange resin (DOWEX 50WX8) for 6 h
(small amount of Pd black observed). The resulting solution was
filtered and solvent was removed. The resulting solid was
dissolved in CH2Cl2 (20 mL) with NEt3 (3 mL, large excess),
4-dimethylaminopyridine (0.005 g, cat., 0.04 mmol), and
TMS-capped-3-isocyanatopropyl-1-silica (1 g) and was stirred
at reflux for 24 h. The mixture was filtered hot, then washed with
Acknowledgment. The Dutch Technology Foundation
(STW) is thanked for financial support (A.R.McD. grant
STW-05772). Dr J. H. Bitter, Utrecht University, is
thanked for his help with surface area measurements.
Dr. J. Hollander, Leiden University, is thanked for his
help with solid-state NMR measurements.