Platinum complex-catalyzed hydrosilylation of 2,2-diaryl-1-methylenecyclopropane affording (silylmethyl)cyclopropane

Article abstract of DOI:10.1016/S0040-4039(02)00165-X

PtI₂(PPh₃)₂-catalyzed hydrosilylation of 2,2-diphenyl-1-methylenecyclopropane with HSiEt₃ forms (2,2-diphenylcyclopropyl)methyl(triethyl)silane in 87% yield as a sole product. This highly selective addition of S

Full text of DOI:10.1016/S0040-4039(02)00165-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 2059–2061
Platinum complex-catalyzed hydrosilylation of
2
,2-diaryl-1-methylenecyclopropane affording
(silylmethyl)cyclopropane
Yasushi Nishihara, Masumi Itazaki and Kohtaro Osakada*
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
Received 14 December 2001; revised 16 January 2002; accepted 18 January 2002
Abstract—PtI (PPh ) -catalyzed hydrosilylation of 2,2-diphenyl-1-methylenecyclopropane with HSiEt forms (2,2-diphenylcyclo-
2
3 2
3
propyl)methyl(triethyl)silane in 87% yield as a sole product. This highly selective addition of SiꢀH bond converts 2,2-diaryl-1-
methylenecyclopropane into its silylated derivative without ring-opening. © 2002 Elsevier Science Ltd. All rights reserved.
1
11
Methylenecyclopropanes are reactive owing to the
58% (Pt(PPh ) ). Table 1 summarizes the reactions of
3 4
presence of an olefinic moiety and to the high strain
energy of the molecule, and are utilized as building
blocks of versatile synthetic organic reactions. Single
bond addition of organic molecules (XꢀY) to
methylenecyclopropane promoted by transition metal
complexes causes functionalization accompanied by
2,2-disubstituted-1-methylenecyclopropanes with vari-
ous organosilanes. The reaction catalyzed by
PtI (PPh ) in toluene (0.07 M substrate) produces 1,1-
diphenyl-1,3-butadiene (10%), which causes a decrease
of the yield of 1a to 74%.
2
3 2
2
–8
ring-opening (Scheme 1 (i)).
Addition to the CꢁC
double bond of methylenecyclopropanes, shown in
Scheme 1 (ii), forms a functionalized cyclopropane
9
derivative. Such a reaction, however, was reported
only as a minor side-reaction of the XꢀH addition to
2,3,6
methylenecyclopropanes.
In this paper we report Pt
complex-catalyzed hydrosilylation of 2,2-disubstituted-
-methylenecyclopropanes, affording the silylated
1
cyclopropanes in high yields and selectivity.
The reaction of triethylsilane with 2,2-diphenyl-1-
methylenecyclopropane in the presence of PtI (PPh )
2
3 2
(
3 mol%) at 140°C afforded (2-triethylsilylmethyl)-1,1-
10
diphenylcyclopropane (1a) in 87% yield (Scheme 2).
1
The H NMR spectrum of the reaction mixture showed
no formation of other possible cyclic and acyclic
organosilanes. The use of hydrido(halogeno)platinum
complexes gave rise to the formation of 1a in compara-
Scheme 1.
Scheme 2.
ble
yields,
87%
(Pt(H)I(PPh ) )
and
85%
3
2
(
Pt(H)Cl(PPh ) ). Other platinum catalysts led to for-
3
3
mation of 1a in lower yields, 67% (PtCl (PPh ) ) and
2
3 2
Keywords: cyclopropanes; silicon and compounds; addition reactions;
platinum; Thorpe–Ingold effect.
*
Corresponding author. Tel.: +81-45-924-5224; fax: +81-45-924-5224;
e-mail: kosakada@res.titech.ac.jp
0
040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00165-X

2
060
Y. Nishihara et al. / Tetrahedron Letters 43 (2002) 2059–2061
a
Table 1. Platinum-catalyzed hydrosilylation of methylenecyclopropanes with hydrosilanes
Entry
Methylenecyclopropane
R2
Hydrosilane
Product
R1
1
Yield (%)b
2
Yield (%)b
1
2
3
4
5
6
7
8
9
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
HSiEt3
HSiPh3
1a
1b
1c
1d
1e
87
53
85
81
81
0
HSiEt Ph
2
HSiPhCl2
HSiCl3
HSi(OEt)3
HSiMe (OEt)
0
2
C H F-4
C H F-4
HSiEt3
HSiEt3
HSiEt3
HSiEt3
1f
1g
1h
80
46
27
0
6
4
6
4
(CH ) Ph
Ph
Ph
(CH ) Ph
Me
H
2g
2h
2i
40
40
57
2
2
2 2
1
1
0c
1
a
Reactions of disubstituted methylenecyclopropane with hydrosilane (1:2) were carried out in the presence of 3 mol% of PtI (PPh ) without
2
3 2
solvent at 80°C for 4 h (entry 4), for 1 h (entry 5), or at 140°C for 1 h (other entries).
Isolated yields, unless otherwise specified.
Two diastereomers of 1h (1:1) and isomeric products 1h and 2h were not separated.
b
c
The reaction of triorganosilanes with 2,2-diaryl-1-
methylenecyclopropane produces the (silylmethyl)-
cyclopropanes as a sole product in 53–87% yields
related to the reactions in this study. The reaction of
the substrate with alkyl substituents at the cyclopropyl
group initially forms the intermediate (A), which under-
goes silylation of the intermediate accompanied by CꢀC
bond cleavage of the three-membered ring via b-alkyl
(
entries 1–3 and 8). Chlorosilanes, such as HSiPhCl2
and HSiCl , yielded analogous hydrosilylation products
3
15
1
d and 1e in 81 and 81% yields, respectively (entries 4
elimination. b-Alkyl elimination of the cyclopropyl-
methyl complex was proposed to be involved in the
ring-opening of 2,2-diaryl-1-methylenecyclopropanes,
giving 1,1-diaryl-1,3-butadienes, promoted by a hydri-
and 5). Alkoxysilanes HSi(OEt) and HSiMe (OEt) did
3
2
not cause the hydrosilylation. The methylenecyclo-
propanes bearing a 2-phenethyl or methyl substituent at
2
-position afforded mixtures of (silylmethyl)-
16
dorhodium complex. The above kinetic reason for
cyclopropane 1 and 3-butenyl(triethyl)silane 2 (entries 9
and 10). The latter product is formed via hydrosilyla-
tion accompanied by ring opening. 2-Phenyl-1-
retaining the cyclopropyl group in the Pt-catalyzed
hydrosilylation seems to be as important as the thermo-
dynamic stability of disubstituted 17cyclopropanes,
explained by the Thorpe–Ingold effect.
methylenecyclopropane reacts with HSiEt to give the
3
ring-opened product 2i exclusively (entry 11).
Scheme 3 depicts the transformation of 1e into cyclo-
propane derivatives with other functional groups. Fluo-
rination and alkoxylation lead to the fluorosilane 3 and
1
2
13
alkoxysilane 4, respectively. Tamao oxidation of 1e
using H O , KF and KHCO gave (2-hydroxymethyl)-
2
2
3
1,1-diphenylcyclopropane (5) in 76% yield.
The hydrosilylation product presented in this study is
accounted for by the reaction mechanism shown in
Scheme 4. Simple Chalk–Harrod type hydrosilylation
of methylenecyclopropane via intermediate (A) (Scheme
1
4
4)
forms the (cyclopropylmethyl)silanes that are the
products of the reactions in Table 1 (entries 1–5 and 8).
Although the addition of a HꢀSi bond in the modified
Chalk–Harrod manner via intermediate (B) would also
give the same product, it is much less favorable due to
steric congestion of the intermediate. Other possible Pt
species (A%) and (B%) via addition of HꢀPt or SiꢀPt
bonds do not give the products in Table 1; they are not
Scheme 3. Reagents and conditions: (i) CuF ·2H O, Et O,
2
2
2
0°C, 2 h; (ii) EtOH, NEt , rt, 16 h; (iii) H O , KF, KHCO ,
3
2
2
3
rt, 12 h.

Y. Nishihara et al. / Tetrahedron Letters 43 (2002) 2059–2061
2061
9
. Addition of silyl compounds to bicyclopropylidene was
reportedtotakeplacewithoutring-opening, see:Pohlmann,
T.; de Meijere, A. Org. Lett. 2000, 2, 3877.
10. Representative procedure for hydrosilylation of methylene-
cyclopropane: Synthesis of 1a. The mixture of 2,2-diphenyl-
1-methylenecyclopropane (619 mg,
3
mmol) and
triethylsilane (698 mg, 6 mmol), and PtI (PPh ) (87 mg,
2
3 2
0.09 mmol, 3 mol%) was heated to 140°C under argon in
a pressure vial. The reaction mixture was diluted with ether
and passed through a Celite pad to remove insoluble
materials. Evaporation of volatiles afforded a brown oil.
Column chromatography (silica gel, hexane, R =0.56) gave
f
colorless oil. Bulb to bulb distillation (180–190°C/3 Torr)
1
gave 1a (840 mg, 87% yield) as colorless oil. H NMR
(
CDCl , 300 MHz): l −0.11 (dd, J=14.7 Hz, 11.7 Hz, 1H),
3
0.69 (q, J=8.0 Hz, 6H), 1.05 (t, J=8.0 Hz, 9H), 1.05–1.10
(
(
overlapped, 1H), 1.24 (dd, J=6.0 Hz, 5.1 Hz, 1H), 1.47
dd, J=8.7 Hz, 5.1 Hz, 1H), 1.71 (dddd, J=11.7 Hz, 8.7
13
1
Hz, 6.0 Hz, 3.0 Hz, 1H), 7.20–7.48 (m, 10H); C{ H} NMR
CDCl , 75.3 MHz): l 3.50, 7.46, 13.49, 22.74, 23.05, 35.25,
(
3
1
25.38, 126.12, 127.40, 128.12, 131.02, 141.79, 147.83; IR
Scheme 4.
(
KBr): 3083, 3060, 3025, 2998, 2953, 2874, 1599, 1495, 1456,
−
1
1445, 1416, 1238 cm . Anal. calcd for C H Si: C, 81.92;
22 30
Insummary, wediscoveredanewmethodologytoprepare
H, 9.37. found: C, 81.91; H, 9.12.
(
cyclopropylmethyl)silanes via hydrosilylation of 2,2-dis-
1
1. Several other catalysts were found to be ineffective for the
ubstituted methylenecyclopropanes catalyzed by the Pt
complex. It is in sharp contrast to Rh-catalyzed hydrosi-
lylation of methylenecyclopropanes, which mainly pro-
formation of 1a: H PtCl (7%), Pd–C (0%), Pd(PPh ) (0%),
Ni(cod) (cod=1,5-cyclooctadiene) (trace), and Ni(PPh )
(0%).
2
6
3 4
2
3 4
8
vides the open-chain products.
1
2. Tamao, K.; Kakui, T.; Akita, M.; Iwahara, T.; Kanatani,
R.; Yoshida, J.; Kumada, M. Tetrahedron 1983, 39, 983.
3. (a) Tamao, K.; Ishida, N.; Tanaka, T.; Kumada, M.
Organometallics 1983, 2, 1694; (b) Tamao, K.; Ishida, N.
J. Organomet. Chem. 1984, 269, C37; (c) Tamao, K.;
Nakajo, E.; Ito, Y. J. Org. Chem. 1987, 52, 4412; (d) Tamao,
K. In Organosilicon and Bioorganosilicon Chemistry;
Sakurai, H., Ed.; Ellis Horwood: Chichester, 1985; p. 231.
4. (a) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87,
1
Acknowledgements
This work was partially supported by a Grant-in-aid for
Scientific Research for Young Chemists No. 13740412
and for Scientific Research on Priority Areas, ‘Molecular
Physical Chemistry’ No. 11166221, from the Ministry of
Education, Culture, Sports, Science and Technology,
Japan.
1
16; (b) Ojima, I.; Fuchikami, T.; Yatabe, M. J. Organomet.
Chem. 1984, 260, 335; (c) Sakaki, S.; Mizoe, N.; Sugimoto,
M. Organometallics 1998, 17, 2510.
1
5. For leading references on b-alkyl elimination, see:
Murakami, M.; Ito, Y. In Activation of Unreactive Bonds
and Organic Synthesis; Murai, S., Ed.; Springer: Berlin
1999; Vol. 3, pp. 97–129. See also: (a) Thomson, S. K.;
Young, G. B. Organometallics 1989, 8, 2068; (b) Thomas,
B. J.; Noh, S. K.; Schulte, G. K.; Sendlinger, S. C.;
Theopold, K. H. J. Am. Chem. Soc. 1991, 113, 893; (c)
Alkianiec, B.; Christou, V.; Hardy, D. T.; Thomson, S. K.;
Young, G. B. J. Am. Chem. Soc. 1994, 116, 9963; (d) Suzuki,
H.; Tanaka, M.; Takemori, T. J. Am. Chem. Soc. 1994, 116,
10779; (e) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.;
Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406; (f)
Hartwig, J. F.; Andersen, R. A.; Bergman, R. G. J. Am.
Chem. Soc. 1989, 111, 2717; (g) McNeill, K.; Andersen, R.
A.; Bergman, R. G. J. Am. Chem. Soc. 1997, 119, 11244.
(h) Kaplan, A. W.; Bergman, R. G. Organometallics 1997,
16, 1106.
References
1
. (a) Brandi, A.;Goti, A. Chem. Rev. 1998, 98, 589; (b) Binger,
P.; B u¨ ch, H. M. Top. Curr. Chem. 1987, 135, 77; (c) Ohta,
T.; Takaya, H. In Comprehensive Organic Synthesis; Trost,
B. M., Ed.; Pergamon: Oxford, 1991; Vol. 5, p. 1185.
. R Si–CN: Chatani, N.; Takeyasu, T.; Hanafusa, T. Tetra-
hedron Lett. 1988, 29, 3979.
. R Sn–H: Lautens, M.; Meyer, C.; Lorenz, A. J. Am. Chem.
Soc. 1996, 118, 10676.
. R N–H: (a) Tsukada, N.; Shibuya, A.; Nakamura, I.;
Yamamoto, Y. J. Am. Chem. Soc. 1997, 119, 8123; (b)
Nakamura, I.; Itagaki, H.; Yamamoto, Y. J. Org. Chem.
2
3
4
3
3
2
1
998, 63, 6458.
5
6
7
8
. RO–H: Camacho, D. H.; Nakamura, I.; Saito, S.;
Yamamoto, Y. Angew. Chem., Int. Ed. 1999, 38, 3365.
. R B–BR : Ishiyama, T.; Momota, S.; Miyaura, N. Synlett
2
2
1
999, 1790.
16. Nishihara, Y.; Yoda, C.; Osakada, K. Organometallics
2001, 20, 2124.
17. (a) Beesley, R. M.; Ingold, C. K.; Thorpe, J. F. J. Chem.
Soc. 1915, 107, 1080; (b) Ingold, C. K. J. Chem. Soc. 1921,
119, 951; (c) Kon, G. A. R.; Steveson, A.; Thorpe, J. F.
J. Chem. Soc. 1922, 121, 650.
. R Si–BR : Suginome, M.; Matsuda, T.; Ito, Y. J. Am.
Chem. Soc. 2000, 122, 11015.
. R Si–H: Bessmertnykh, A. G.; Blinov, K. A.; Grishin, Yu.
K.; Donskaya, N. A.; Tveritinova, E. V.; Yur’eva, N. M.;
Beletskaya, I. P. J. Org. Chem. 1997, 62, 6069.
3
2
3