11134
J. Am. Chem. SOC.1995,117, 11134-11141
Addition of Ketene Silyl Acetals to the Triplet Excited State of C ~ via O Photoinduced Electron Transfer Leading to the Fullereneacetates Koichi Mikami,**tShoji Matsumoto? Akito Ishida? Setsuo Takamuku,* Tomoyoshi Suenobu? and Shunichi Fukuzumi*98 Contribution from the Department of Chemical Technology, Faculty of Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo 152, Japan, The Institute of Scient@c and Industrial Research, Osaka University, Ibaraki, Osaka 567, Japan, and Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan Received July 12, 1995@
Abstract: The photochemical carbon-carbon bond formation of C a with ketene silyl acetals is described to give a new way for fullerene functionalization chemistry. The photoaddition of ketene silyl acetals to Cm occurs efficiently under irradiation of the visible light in benzene as well as benzonitrile to yield the fullereneacetates. The comparison of the observed rate constants determined from the dependence of the quantum yields on the concentrations of ketene silyl acetals as well as the quenching of triplet excited state of Cm by ketene silyl acetals with those predicted for the electron transfer processes indicates that the photoaddition proceeds via photoinduced electron transfer from ketene silyl acetals to the triplet excited state of Cm. The negative shift in the one-electron reduction potentials by the adduct formation of Cm is examined by the cyclic voltammetry measurements. The factors to control the formation of mono- and bisadducts of c 6 0 are clarified based on the rates of photoinduced electron transfer from ketene silyl acetals to the triplet excited states of CW and the adducts.
Introduction Since the preparation of buckminsterfullerene (C,) in synthetically useful quantities,’ much attention has been focused on its functionalization with nucleophiles, radicals, reducing agents, dienes, dipoles, zero-valent transition metals, oxygen, and also electrophiles.* Ester-derived ketene silyl acetals (KSAs) may be regarded as attractive nucleophiles for the functionalization of C60, since KSAs can be used as storable enolate equivalents in the Aldol3 and Michael4 processes for C-C bond formation to yield the adducts with ester functionalTokyo Institute of Technology. The Institute of Scientific and Industrial Research, Osaka University. 8 Faculty of Engineering, Osaka University. Abstract published in Advance ACS Abstracts, November 1, 1995. (1) Hirsch, A. The Chemistry of the Fullerenes; Thieme: Stuttgart, 1994. Kratschmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman, D. R. Nature 1990, 347, 354. Haufler, R. E.; Conceicao, J.; Chibante, L. P. F.; Chai, Y.; Byme, N. E.; Flanagan, S.; Haley, M. M.; O’Brien, S. C.; Pan, C.; Xiao, Z.; Billups, W. E.; Ciufolini, M. A.; Hauge, R. H.; Margrave, J. L.; Wilson, L. J.; Curl, R. F.; Smalley, R. E. J . Phys. Chem. 1990, 94, 8634. Kroto, H. W.; Heath, J. R.; O’Brien, S. C.; Curl, R. F.: Smallev, R. E. Nature 1985, 318, 162. Also see: Osawa, E. Kagaku (Chemistj) 1970, 25, 854. Chem. Abstr. 1971, 74(8): 75698~. (2) Reviews: Hammond, G. S.; Kuck, V. J. ACS Symp. Ser. 1992, Vol. 481. Suzuki, T.; Li, Q.;Khemani, K. C.; Wudl, F.; Almarsson, 0. Science 1991, 254, 1186. Wudl, F. Acc. Chem. Res. 1992, 25, 157. Miller, P. G. Chem. Ind. 1993, 226. Taylor, R.: Walton, D. R. M. Nature 1993, 363, 685. Hirsch, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1138. Diederich, F.; Isaacs, L.; Philp, D. Chem. SOC. Rev. 1994, 243. (3) Reviews: Mukaiyama, T. Org. React. 1982, 28, 203. Evans, D. A,; Nelson, J. V.; Taber, T. R. Top. Stereochem. 1982, 13, 1. Heathcock, C. H. Asymmetric Synthesis; Momson, J. D., Ed.; Academic Press: New York, 1984; Vol. 3, Chapter 2. Masamune, S.; Choy, W.; Peterson, J. S.; Sita, L. R. Angew. Chem., Int. Ed. Engl. 1985, 24, 1. Paterson, I . ; Goodman, J. M.; Lister, M. A.; Schumann, R. C.; McClure, C. K.; Norcoss, R. D. Tetrahedron 1990, 46, 4663. Gennari, C. Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: London, 1991; Vol. 2, Chapter 2.4. (4) Reviews: Oare, D. A.; Heathcock, C. H. Top. Stereochem. 1989, 19, 227. Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis; Pergamon Press: Oxford, 1992; Chapter 2. +
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ity. However, no “silatropic ene rea~tion’’,~ in other words, [1,5]-silyl transfer from KSAs to c 6 0 has observed6 in contrast with the analogous “prototropic ene reaction”, an intermolecular [1,5]-hydrogen transfer process.’ On the other hand, electron transfer oxidation of KSAs has recently received increasing attention in both thermal and photochemical reactions because of its synthetic utility for the C-C bond The use of the excited state of a substrate is of particular interest, since it has recently been reported that addition of KSA to 10methylacridone proceeds efficiently via the photoinduced electron transfer from KSA to the triplet excited state of 10methylacridone under neutral conditions without acid or base catalysts under irradiation of the visible light.’O The oneelectron reduction potential of the triplet excited state of Cm (1.14 V vs SCE) reported by Foote et al.” is more positive than that of 10-methylacridone (0.88 V vs SCE).’O Thus, the ( 5 ) Mikami, K.; Matsukawa, S. J . Am. Chem. Soc. 1994, 116, 4077.
(6) Nihon Kogyo Shinbun, Aug. 5th, 1994. Mikami, K.; Matsumoto, S. Annual Meeting of the Chemical Society of Japan, Nagoya, October 1-4, 1994. Abstract No. 4D310. Mikami, K.; Matsumoto, S. Synlett 1995, 229. (7) Wu, S.; Shu, L.; Fan, K. Tetrahedron Lett. 1994,35, 919. Komatsu, K.; Murata, Y.; Sugita, N.; Wan, T. S. M. Chem. Lett. 1994, 63. Reviews on ene reactions: Mikami, K.; Shimizu, M. Chem. Rev. 1992, 92, 1021. Snider, B . B. Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: London, 1991; Vols. 2 and 5. Hoffmann, H. M. R. Angew. Chem., Int. Ed. E n d . 1969. 8. 556. (8) Fukuzumi, i;Fujita, M.; Otera, J.: Fujita, Y . J . Am. Chem. Soc. 1992, 114, 10271. (9) Reetz, M. T.; Schwellnus, K.; Hiibner, F.; Massa, W.; Schmidt, R. E. Chem. Ber. 1983, 116, 3708. Totten, G. E.; Wenke, G.; Rhodes, Y. E. Synth. Commun. 1985, 15, 291. Bhattacharya, A.; DiMichele, L. M.; Dolling, U.-H.; Grabowski, E. J. J.; Grenda, V. J. J . Org. Chem. 1989, 54, 6118. Sato, T.; Wakahara, Y.; Otera, J.; Nozaki, H.; Fukuzumi, S. J . Am. Chem. SOC. 1991, 113, 4028. Otera, J.; Fujita, Y.; Sato, T.; Nozaki, H.; Fukuzumi, S.; Fujita, M. J. Org. Chem. 1992, 57, 5054. Odenkirk, W.; Whelan, J.; Bosnich, B. Tetrahedron Lett. 1992, 33, 5729. Rathore, R.; Lin, Z . ; Kochi, J. K. Tetrahedron Lett. 1993,34, 1859. Fukuzumi, S.; Fujita, M.; Matsubayashi, G.; Otera, J. Chem. Lett. 1993, 1451. Shu, L.-H.; Wang, G.-W.; Wu, S.-H.; Wu, H.-M. J . Chem. Soc., Chem. Commun. 1995, 367. (10) Fukuzumi, S.; Fujita, M.; Otera, J. J . Org. Chem. 1993, 58, 5405.
0002-7863/95/1517-11134$09.00/00 1995 American Chemical Society
C-C Bond Formation of COO wirh Kerene Si/d Acetals
J. Am. Chem. Sric., Vi>/.117, No. 45. 1995 11 135
photoinduced electron transfer from KSAs to the triplet excited state 'Cm* is energetically feasible."." However, the valuable role of photoinduced electron transfer processes of CMlfor its functionalization has remained to be explored. We repott herein the photoinduced electron transfer process from KSAs to which 'Cmi 0.1.; to give the fullerene with ester f~nctionality,~~." is useful for further elaboration to fullerene amide and peptide of biological impottance.l" The rates of photoinduced electron transfer from various KSAs to the triplet excited states of and its derivatives have been determined from the dependence of quantum yields on the KSA concentrations as well as the quenching of the triplet excited states by KSAs, providing valuable insight into the mechanistic viability and the fine control of degree of the functionalization of Ch0.
Table 1. Photoinduced C-C Bond Formation of C,,Swith Ketene Silyl Acetals
entry
%NU
Yield 01 monoadducl'
Equiv.
Time (mi")
Product
p*)
20
90
2a
71 (1001
10
30
IO
120
10
90
10 3
60
10
30
10
60
l a OE' 2
44 11001
+;;Me#"
2.
63 (1001
2b
36 1561
*a'
Results and Discussion Photnaddition of Ketene Silyl Acetals. CMl(20 mg) and an excess amount of ethyl acetate-derived KSA l a (H?C=C(0Et)OSiMez) (20 equiv) in benzene (20 mL) were photolyzed with a high-pressure mercury lamp (eq I ) . l 7 The color of the solution changed from purple to dark brown within 2 h. In the
5
7 B
"we
io
26 I601
gmY'
31 (50) 25
28 I461
IC' +
111
4OsiMe3
VEt I*
C.
2a
dark. however, no reaction has occurred even at 200 "C. Purification through flash column chromatography on silica gel (hexanes and then mixtures of hexanes and ethyl acetate) afforded the product. ethyl 1,2-dihydro[601fullerene-I-acetate 2a in 71% yield which corresponds to the quantitative yield t I II .Arhor.i\t. J. \\.: Fuote. C. S.: K m . M. J . A m C b r m . S w 1992. 114. 1177. t 111Photomiuced C I W O ~ transfer rractions o i iuiiermes: Kamat. P. \ . J . :In,. Chcwi. So.. 1991. 113. 9705, Kmsic. P. J.: Wassrrman. E.: P x k i n w n . B. .A: Malone. B.: Holler. E. R.. Jr.: Keifer. P. N.: Munon. J. R.: Prrsmn. K. F. J. Anr, C b r m Sot. 1991. 11.3. 6274. Vrrhocven. 1. W.: Sshrrer. T.: Hc>m;mn. D. K e d T r a v Clzirn. P ~ r w B o i1991. 110. 149. Srn&m R. J.: Srarka. A. Z.: Smith. G. R.: Hochrtrarser. R. M. ChC=C(OMe)OSiMei) (entries 6-X). The initial pho. this toproduct is identified as CWI ,2-(H)CMe>COOMe( 2 ~ ) In case, however, the initial monoadduct is further reacted to yield the bisadduct (3c: A,,,;,, = 432 nm) at prolonged irradiation time particularly in higher concentration (1.5 x IO-' M) of the KSA l e (entry 6 ) . Short time irradiation leads to the drastic increase in the yield of 2c based on recovered CM(entry 7). The addition of rerr-butyldimethylsilyl KSA (IC') was found to be relatively slow (entry 9). Unfortunately, the silyl enol ether of acetone and allylic silanes did not undergo the addition reaction (entries 10 and 11). Essentially the same products are obtained in photochemical reactions of CNI with KSAs in benzonitrile as well. No photochemical reactions of Cn, with benzyltrimethylsilane and allyltrimethylsilane have occurred under irradiation with the visible light. Judging from the reported values of one-electron (16) Fullerme-peptide: Pr;iIo. M.: Bianco. A,: Maggini. M.: Sconano. G.: Toniolo. C.: Wudl. F. J . 0,y. Ch.1993. 58. 5578. Wimg. N . : LI. J.: Zhu. D.: Chan. T . H. T e w o h m h , t 1995. 36. 43 I . Fullcrcne-amide: Sijhesma. R.: Snlanov. G.: Wudl. F.: Castonr. J . A,: Wilkins. C.: Friedman. S. H.: Decamp. D. L.: Kenyon. G. L. J . A m C l w n S w . 1993. 115. 6SIO. Zhang. X.: Romem. A,: Foote. C. S. .I. A m Clwm $or. 1992. 115. I102.I. Skiehe. A,: Hirrch. A. 1. Ch
