to be very efficient under our standard conditions leading to
more than 95% yield after 24 h. Then, PtO , which was to
our knowledge never tested as a hydrosilylation catalyst, gave
remarkable results similar to those observed for Pt/C.
2
Table 1. Hydrosilylation of Allylamine with
Methyldiethoxysilane in the Presence of Various Catalysts
2
These results prompted us to investigate PtO further in
order to evaluate its scope and limitations for other substrates
containing amino functions.
In Table 2, the performances of PtO
are compared. As a general trend, PtO
2
and Speier’s catalyst
led to total conversion
2
Table 2. PtO
Aminated Alkenes with Methyldiethoxysilane in 24 h
2
vs H
2
PtCl
6
2
‚6H O for Hydrosilylation of
a
1
Calculated on the basis of H NMR spectrum.
Results are summarized in Table 1. All catalysts were tested
8
under standard hydrosilylation conditions. Equimolar amounts
of silane and alkene are stirred with 100 ppm (i.e., 100 µmol
9
per mole of silane) of catalyst at 85 °C in a sealed tube. As
a general trend, carrying out the reaction in a classical round-
bottom flask led to lower yield and poor reproducibility.
Speier’s catalyst gave only moderate yields and low
reproducibility probably as a result of poisoning of the
catalyst by the amino function. Karstedt’s catalyst (Table 1,
entry 2), under similar conditions, gave identical and highly
reproducible results. This could be attributed to the higher
1
0
stability of the platinum complexes toward strong ligands.
Both catalysts gave γ and â regioisomers in over 95/5 ratios
but in moderate yields.
Next, we tested heterogeneous catalysts, which are very
little used for hydrosilylation reaction despite their easy
removal from the reaction medium by simple filtration. First,
a
Calculated on the basis of 1H NMR spectrum. b Reactions run with
Pt/C and (Bu4N)2PtCl6 gave around 90% conversion of pure γ adduct.
1
1
Pt/C, which was described for hydrosilylation of alkynes,
12
in accordance with the early work of Wagner, proved also
(
7) (a) Marciniec, B.; Gulinski, J.; Urbaniak, W.; Nowicka, T.; Mirecki,
Table 3. Hydrosilylation Conversion with
Methyldiethoxysilane on Various Functionalized Alkenes
J. Appl. Organomet. Chem. 1990, 4, 27. (b) Ryan, J. W.; Speier, J. L. J.
Org. Chem. 1966, 31, 2698. (c) Coy, D. H.; Fitton, F.; Haszeldine, R. N.;
Newslands, M. J.; Tipping, A. E. J. Chem. Soc., Dalton Trans. 1974, 1852.
(8) (a) Coy, D. H.; Fitton, F.; Haszeldine, R. N.; Newlands, M. J.;
Tipping, A. E. J. Chem. Soc., Dalton Trans. 1974, 1852. (b) Seyferth, D.;
Washburne, S. S.; Attridge, C. J.; Yamamoto, K. J. Am. Chem. Soc. 1970,
9
2, 4405. (c) Seyferth, D.; Prud’homme, C. C.; Wang, W.-L. J. Organomet.
Chem. 1984, 277, 203.
9) Procedure for 3-(diethoxy-methyl-silanyl)-1-acetoxy-propane: 1.6
(
mL (10 mmol, 1 equiv) of methyldiethoxysilane and 1.08 mL (10 mmol, 1
equiv) of allyl acetate are stirred without solvent in a sealed tube under
argon without any previous purification. Platinum oxide, PtO2 (100 ppm
equiv) is added, and the tube is sealed and heated at 85 °C during 20 h.
After cooling to room temperature, the crude is filtered through activated
charcoal with anhydrous ethanol. The filtrate is concentrated, dried under
reduced pressure, and purified by vacuum distillation to afford the desired
1
product in 80% yield. H NMR (300 MHz, CDCl3): δ 0.13 (s, 3H, CH3-
Si); 0.63 (m, 2H, SiCH2); 1.22 (t, 6H, J ) 7.1 Hz, OCH2CH3); 1.70 (m,
2
H, SiCH2CH2CH2); 2.05 (s, 3H, CH3COO); 3.77 (q, 4H, J ) 7.1 Hz, OCH2-
13
CH3); 4.03 (t, 2H, J ) 7.0 Hz, SiCH2CH2CH2). C NMR (50 MHz;
CDCl3): δ -5.0 (s); 9.9 (s); 18.3 (s); 20.9 (s); 22.2 (s); 58.1 (s); 66.6 (s);
2
9
1
70.0 (s). Si NMR (59 MHz, CDCl3 + Cr(acac)3 0.03 M): δ -5.5. IR
-1
(
ATR, neat): ν (cm ) 2970-2880 (C-C); 1735.1 (CdO); 1230 (SiCH3
δ); 1068.3 (Si-O); 942.0 (Si-O); 760.9 (SiCH3 γ). MS (CI, NH3): m/z
+
+
+
2
0
52 (M + NH4 ); 235 (M + H ); 189 (M + H - EtOH). Bp ) 72 °C/
.5 mbar.
(
10) (a) Hitchcock, P. B.; Lappert, M. F.; Warhurst, N. J. W. Angew.
Chem., Int. Ed. Engl. 1991, 30, 438. (b) Karstedt, B. D. U.S. Patent 3,-
14,720, 1974.
11) Chauhan, M.; Hauck B. J.; Keller L. P.; Boudjouk P. J. Organomet.
Chem. 2002, 645, 1.
a
Yield calculated on the basis of H NMR spectrum. b Ratio ω/ω-1 )
1
8
(
90/10, all others are >95/5
2118
Org. Lett., Vol. 4, No. 13, 2002