[107887-79-6]  · C9H8BrLi  · 1-Bromo-1-lithio-2-phenylcyclopropane  · (MW 203.01)

(highly reactive organolithium compound, generated at low temperature in solutions of THF or diethyl ether; reacts with electrophiles at temperatures below -85 °C)

1-Bromo-1-lithio-2-phenylcyclopropane, which is generated in situ by treatment of 1,1-dibromo-2-phenylcyclopropane with Methyllithium, undergoes spontaneous rearrangement to phenylallene under a-elimination of Lithium Bromide (eq 1).1,2

Solutions of 1-bromo-1-lithiocyclopropanes3 can be generated in THF or diethyl ether or in mixtures of THF/diethyl ether and THF/diethyl ether/pentane at -110 to -85 °C. The bromine-lithium exchange of 1,1-dibromocyclopropanes turns out to be the most versatile method. Solutions of 13C,6Li-labeled 1-bromo-1-lithiocyclopropanes have been studied by NMR spectroscopy.4 Solutions of such carbenoids react with a variety of electrophiles. When 1-bromo-1-lithiocyclopropanes are added to benzophenone the formation of cyclobutanones results via a spontaneous rearrangement of oxaspiropentanes (eq 2).5

A stereoselective bromine-lithium exchange occurs upon treatment of 7,7-dibromonorcarane with n-Butyllithium to give exo-7-bromo-endo-7-lithiobicyclo[4.1.0]heptane (eq 3). A slight excess of dibromocyclopropane relative to butyllithium is required to achieve stereoselectivity. The exo-lithium stereoisomer, which is the favored product of a kinetically controlled lithiation, undergoes another bromine-lithium exchange reaction with dibromonorcarane to give ultimately the thermodynamically favored endo-lithium carbenoid (eq 4). The configuration of the latter reagent is proven by carboxylation (eq 3).6

The following representative 1-bromo-1-lithiocyclopropanes have also been prepared by bromine-lithium exchange reactions:12 1-bromo-1-lithio-2-phenylcyclopropane (1),6,7 1-bromo-1-lithio-2,2-dimethylcyclopropane (2),5 13-bromo-13-lithiobicyclo[10.1.0]tridecane (3),8 endo-7-bromo-exo-7-lithio-1-methoxybicyclo[4.1.0]heptane (4),9 exo-9-bromo-endo-9-lithiobicyclo[6.1.0]nonane (5),10 and trans-2-benzyloxymethyl-1-bromo-1-lithiocyclopropane (6).7,11

The treatment of endo-7-bromo-exo-7-(trimethylstannyl)bicyclo[4.1.0]heptane results in an exclusive tin-lithium exchange reaction to give endo-7-bromo-exo-7-lithionorcarane (eq 5).13

Related Reagents.

Cyclopropyllithium; Cyclopropylmagnesium Bromide; 1-Lithio-1-methoxycyclopropane.

1. (a) Moore, W. R.; Ward, H. R. JOC 1962, 27, 4179. (b) Skattebol, L.; ACS 1963, 17, 1683.
2. FF 1967, 1, 686.
3. (a) Köbrich, G. AG(E) 1972, 11, 473. (b) Siegel, H. Top. Curr. Chem. 1982, 106, 55.
4. Seebach, D.; Hässig, R.; Gabriel, J. HCA 1983, 66, 308.
5. (a) Braun, M.; Seebach, D. AG(E) 1974, 13, 277. (b) Braun, M.; Dammann, R.; Seebach, D. CB 1975, 108, 2368.
6. Seyferth, D.; Lambert, R. L., Jr.; Massol, M. JOM 1975, 88, 255.
7. Kitatani, K.; Hiyama, T.; Nozaki, H. BCJ 1977, 50, 3288.
8. Braun, M.; Seebach, D. CB 1976, 109, 669.
9. (a) Taylor, K. G.; Hobbs, W. E.; Clark, M. S.; Chaney, J. JOC 1972, 37, 2436. (b) Taylor, K. G.; Chaney, J. JACS 1976, 98, 4158.
10. Loozen, H. J. J.; Castenmiller, W. A.; Buter, E. J. M.; Buck, H. M. JOC 1976, 41, 2965.
11. (a) Kitatani, K.; Hiyama, T.; Nozaki, H. JACS 1975, 97, 949; (b) Harada, T.; Hattori, K.; Katsuhira, T.; Oku, A. TL 1989, 30, 6035.
12. For further examples of 1-halo-1-lithiocyclopropanes, see: (a) Köbrich, G.; Goyert, W. T 1968, 24, 4327; (b) Taylor, K. G.; Chaney, J. JACS 1972, 94, 8924; (c) Schmidt, A.; Köbrich, G. TL 1974, 2561; (d) Marino, J. P.; Browne, L. J. TL 1976, 3241; (e) Loozen, H. J. J.; Robben, W. M. M.; Buck, H. M. RTC 1976, 95, 245; (f) Müller, C.; Stier, F.; Weyerstahl, P. CB 1977, 110, 124; (g) Kitatani, K.; Yamamoto, H.; Hiyama, T.; Nozaki, H. BCJ 1977, 50, 2158; (h) Sander, V.; Weyerstahl, P. CB 1978, 111, 3879; (k) Hiyama, T.; Kanakura, A.; Yamamoto, H.; Nozaki, H. TL 1978, 3047; (l) Hässig, R.; Siegel, H.; Seebach, D. CB 1982, 115, 1990; (m) Saimoto, H.; Nishio, K.; Yamamoto, H.; Shinoda, M.; Hiyama, T.; Nozaki, H. BCJ 1983, 56, 3093; (n) Seebach, D.; Stucky, G. AG(E) 1988, 27, 1351; (o) Schmidt, A.; Köbrich, G.; Hoffmann, R. W. CB 1991, 124, 1253.
13. Seyferth, D.; Lambert, R. L., Jr. JOM 1975, 88, 287.

Manfred Braun

Heinrich-Heine Universität, Düsseldorf, Germany

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