LETTER
Synthetic Radical Reactions Using Hydrogermanes
3153
(2) Boyer, I. J. Toxicology 1989, 55, 253.
(3) Baguley, P. A.; Walton, J. C. Angew. Chem. Int. Ed. 1998,
37, 3073; and references therein.
(4) (a) Giese, B.; Kopping, B.; Chatgilialoglu, C. Tetrahedron
Lett. 1989, 30, 681. (b) Chatgilialoglu, C. Acc. Chem. Res.
1992, 25, 188. (c) Chatgilialoglu, C.; Guerra, M.; Guerrini,
A.; Seconi, G. J. Org. Chem. 1992, 57, 2427.
2
6
R
R•
Bu2XGe•
E
1
1
6
3 + Bu2XGe•
7 + Bu2XGe•
1
Bu2XGe
Bu2XGe
+
Bu2XGe•
(d) Yamazaki, O.; Togo, H.; Matsubayashi, S.; Yokoyama,
M. Tetrahedron 1999, 55, 3735. (e) Studer, A.; Amrein, S.;
Schleth, F.; Schulte, T.; Walton, J. C. J. Am. Chem. Soc.
2003, 125, 5726.
E
E
8
Scheme 4
(5) (a) Sakurai, H.; Mochida, K.; Hosomi, A.; Mita, F. J.
Organomet. Chem. 1972, 38, 275. (b) Chatgilialoglu, C.;
Ballestri, M. Organometallics 1995, 14, 5017.
(c) Nakamura, T.; Yorimitsu, H.; Shinokubo, H.; Oshima, K.
Bull. Chem. Soc. Jpn. 2001, 74, 747.
(6) For the hydrogermane-mediated intermolecular radical
addition of iodoalkanes, see: (a) Pike, P.; Hershberger, S.;
Hershberger, J. Tetrahedron Lett. 1985, 26, 6289. (b) Pike,
P.; Hershberger, S.; Hershberger, J. Tetrahedron 1988, 44,
6295.
In conclusion, hydrogermanes 1a and 1b are valuable as
radical mediators not only for reduction of haloalkanes
but also for intra- and intermolecular addition of haloal-
kanes to alkenes. We have demonstrated that elaboration
of the substituent on germanium enables fine control of
the reactivity of hydrogermanes.
(7) (a) Inoue, K.; Sawada, A.; Shibata, I.; Baba, A. J. Am. Chem.
Soc. 2002, 124, 906. (b) Hayashi, N.; Shibata, I.; Baba, A.
Org. Lett. 2005, 7, 3093. (c) Takami, K.; Mikami, S.;
Yorimitsu, H.; Shinokubo, H.; Oshima, K. Tetrahedron
2003, 59, 6627; and references therein.
Typical Procedure
Under a nitrogen atmosphere, Et3B (1.0 M in hexane, 0.10 mL, 0.10
mmol) and dry air (10 mL) were added to a stirred solution of 2a
(148 mg, 0.50 mmol), 6a (320 mg, 2.50 mmol), and 1b (233 mg,
1.00 mmol) in THF (1.0 mL) at 0 °C. After being stirred for 10 min,
the mixture was warmed to r.t. and stirred for 24 h. The reaction
mixture was treated with sat. aq NaHCO3 (5 mL) and extracted with
t-BuOMe (3 × 10 mL). The extract was dried over Na2SO4 and
evaporated. Purification of the residual oil by silica gel column
chromatography gave tert-butyl pentadecanoate (7a) in 97% yield
(145 mg, 0.485 mmol).
(8) Barton, D. H. R.; Jang, D. O.; Jaszberenyi, J. C. J. Org.
Chem. 1993, 58, 6838; and references therein.
(9) (a) The preparation of 1a was carried out by the following
steps: butylation of GeCl4 with BuMgBr, dealkylative
dichlorination of Bu4Ge with AlCl3 and AcCl, reduction of
Bu2GeCl2 with LiAlH4, and chlorination of Bu2GeH2 with
CuCl2. For the last step, see: Ohshita, J.; Toyoshima, Y.;
Iwata, A.; Tang, H.; Kunai, A. Chem. Lett. 2001, 886.
(b) For the preparation of 1a, see also: Satge, J. Ann. Chim.
1961, 6, 519.
Compound 7a
IR (neat): 2925, 1733, 1153 cm–1. H NMR (CDCl3): d = 0.88 (t,
1
J = 6.3 Hz, 3 H), 1.20–1.30 (m, 24 H), 1.44 (s, 9 H), 2.19 (t, J = 7.5
Hz, 2 H). 13C NMR (CDCl3): d = 14.10 (CH3), 22.67 (CH2), 25.10
(CH2), 28.09 (3 × CH3), 29.09 (CH2), 29.29 (CH2), 29.35 (CH2),
29.47 (CH2), 29.60 (CH2), 29.64 (2 × CH2), 29.67 (2 × CH2), 31.91
(CH2), 35.61 (CH2), 79.84 (C), 173.34 (C). MS: m/z (relative inten-
sity) = 243 (9.5) [M+ – C4H7], 242 (4.7) [M+ – C4H8], 57 (100).
(10) The use of Bu2SnH2 as reducing agent was also attempted for
the reduction of 2a. The Et3B-initiated reaction with
Bu2SnH2 (1.2 equiv) for 24 h gave 3a in 34% yield with
recovery of 2a (ca. 50%).
(11) (a) Newcomb, M.; Horner, J. H.; Filipkowski, M. A.; Ha, C.;
Park, S.-U. J. Am. Chem. Soc. 1995, 117, 3674.
(b) Gualtieri, G.; Geib, S. J.; Curran, D. P. J. Org. Chem.
2003, 68, 5013.
Acknowledgment
(12) Newcomb, M. In Radicals in Organic Synthesis, Vol. 1;
Renaud, P.; Sibi, M. P., Eds.; Wiley-VCH: Weinheim, 2001,
Chap. 3.1, 317.
This work was partly supported by Grants-in-Aid for Scientific Re-
search from the Ministry of Education, Culture, Sports, Science,
and Technology, Government of Japan.
(13) The reported value for kH(1c) at 80 °C is 3.8 × 105 M–1s–1.
See: Chatgilialoglu, C.; Ballestri, M.; Escudié, J.; Pailhous,
I. Organometallics 1999, 18, 2395.
References
(1) (a) Renaud, P.; Sibi, M. P. Radicals in Organic Synthesis;
Wiley-VCH: Weinheim, 2001. (b) Curran, D. P.; Porter, N.
A.; Giese, B. Stereochemistry of Radical Reactions; VCH:
Weinheim, 1996. (c) Curran, D. P. In Comprehensive
Organic Synthesis, Vol. 4; Trost, B. M.; Fleming, I., Eds.;
Pergamon Press: Oxford, 1991, Chap. 4.1 and 4.2, 715.
(d) Giese, B. Radicals in Organic Synthesis: Formation of
Carbon–Carbon Bonds; Pergamon Press: Oxford, 1986.
Synlett 2005, No. 20, 3151–3153 © Thieme Stuttgart · New York