5464
The general aspects of ortho-metalation reactions have been reviewed elsewhere.11 To gain
more information about this special directed ortho-metalation Ph3P-CHMe (8) and Ph3P-
CHSiMe3 (9) were reacted with t-BuLi/hexane in THF at ^78ꢀC. It was found that the sterically
hindered and less acidic ylide 8 reacts readily with t-BuLi, but at higher temperatures (^40ꢀC)
than 1 to give an ortho-metalated species.k The electronically stabilised and probably more acidic
ylide Ph3P-CHSiMe3 (9) does not react with t-BuLi even at room temperature. This is in accord
with the point of view that the ortho-metalation is strongly dependent on pre-coordination of the
ylide function to Li+. If the coordination is hindered t-BuLi is not directed to the kinetically
favoured ortho position of the aromatic ring system. Similar observations have been made in
ortho-metalation reactions of phosphine oxides and phosphine imides which are isolelectronic to
phosphorus ylides.12,13
Acknowledgements
Financial support from the Graduiertenkolleg `Metallorganische Chemie' Marburg (scholarship
for Karsten Korth), DFG (SFB 260) and the `Fonds der Chemischen Industrie' is gratefully
acknowledged.
References
1. Cristau, H. J. Chem. Rev. 1994, 94, 1299±1313.
2. Corey, E. J.; Kang, J. J. Am. Chem. Soc. 1982, 104, 4724±4725.
3. Schaub, B.; Jenny, T.; Schlosser, M. Tetrahedron Lett. 1984, 25, 4097±4100.
4. Schaub, B.; Schlosser, M. Tetrahedron Lett. 1985, 26, 1623±1626.
5. Corey, E. J.; Kang, J.; Kyler, K. Tetrahedron Lett. 1985, 26, 555±558.
6. Schlosser, M.; Respondek, J.; Schaub, B.; Tuong, H. B. Chimia 1983, 37, 10±11.
7. Okabe, M.; Sun, R.-C. Tetrahedron Lett. 1993, 34, 6533±6536.
8. Steiner, M.; Grutzmacher, H.; Pritzkow, H.; Zsolnai, L. J. Chem. Soc., Chem. Commun. 1998, 285±286.
9. Goumri-Magnet, S.; Gornitzka, H.; Baceiredo, A.; Bertrand, G. Angew. Chem. 1999, 111, 710±712; Angew. Chem.,
Int. Ed. Engl. 1999, 38, 678±680.
10. Arduengo III., A. J.; Dias, H. V. R.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1992, 114, 5530±5534.
11. Snieckus, V. Chem. Rev. 1990, 90, 879±933.
12. Gray, M.; Chapell, B. J.; Felding, J.; Taylor, N. J.; Snieckus, V. Synlett 1998, 422±424.
13. Steiner, A.; Stalke, D. Angew. Chem. 1995, 107, 1908±1910; Angew. Chem., Int. Ed. Engl. 1995, 34, 1752±1754.
14. Bestmann, H.-J.; Stransky, W.; Vostrowsky, O. Chem. Ber. 1976, 1694±1700.
15. Wingerter, S.; Gornitzka, H.; Bertrand, G.; Stalke, D. Eur. J. Inorg. Chem. 1999, 173±178.
k
Preparation of 8: Same procedure as in y; 100 mg (0.34 mmol) Ph3P-CHMe; 0.22 ml (0.35 mmol, 1.6 M) t-BuLi in
hexane. The reaction was monitored spectroscopically while warming the NMR tube several times for 30 s to room
temperature until 31P spectra indicated complete deprotonation. Slow warming of another sample in the NMR probe
head indicated that the deprotonation reaction starts at ^40ꢀC. 1H NMR (400.13 MHz, THF-d8, ^100ꢀC): ꢀ 8.10
(broad signal, 1H), 7.5±7.1 (broad signal, m, 10 H), 6.8 (broad signal, 1H), 6.65 (broad signal, 1H), 6.55 (broad signal,
1H), 1.45 (d, J(HX)=20.2 Hz, 3H), 0.2 (s, 1H). Comment: Neither at ^40ꢀC nor at ^100ꢀC was high resolution of all
signals achieved. 13C NMR (100.32 MHz, THF-d8, ^100ꢀC): ꢀ 211.4 (dq, J(CP)=50 Hz, J(C7Li)=29 Hz, Cl), 142.1
(d, 3J(CP)=29 Hz, Ca), 139.9 (d, 1J(CP)=117 Hz, Cj), 135.3 (d, 1J(CP)=65 Hz, Ci), 133.5 (d, 2J(CP)=8 Hz, Co), 131.2
(d, 3J(CP)=25 Hz, Cc), 130.2 (d, 4J(CP)=<2 Hz, CP), 128.5 (d, 3J(CP)=9 Hz, Cm), 126.0 (d, 4J(CP)=4 Hz, Cb), 122.2
(d, 2J(CP)=13 Hz, Cd), 35.9 (d, 2J(CP)=19 Hz, P-CHMe), 4.1 (m at ^100ꢀC, d at ^60ꢀC, 1J(CP)=62 Hz, 1J(CH)=137
Hz, P-CHMe). 31P NMR (161.97 MHz, THF-d8, ^100ꢀC): ꢀ 24 (s). 7Li NMR (155.04 MHz, THF-d8, ^100ꢀC): ꢀ 3.8 (s).
2
1