Phenylmagnesium Bromide1

PhMgX
(X = Br)

[100-58-3]  · C6H5BrMg  · Phenylmagnesium Bromide  · (MW 181.32) (X = Cl)

[100-59-4]  · C6H5ClMg  · Phenylmagnesium Chloride  · (MW 136.87)

(adds to many unsaturated functional groups; phenyl can displace halide and like groups; functions as a strong base and a Lewis acid1b-f)

Physical Data: NMR and calorimetric observations indicate that PhMgBr in Et2O and THF and PhMgCl in THF are actually mixtures of PhMgX, Ph2Mg, and MgX2.2,3 Although PhMgBr and PhMgCl are essentially monomeric in THF, PhMgBr is associated significantly in Et2O except at low concentrations.3,4 Solids isolated include PhMgBr(Et2O)25 and PhMgBr(THF)2,6 both shown by X-ray diffraction studies to have four-coordinate Mg.

Solubility: both sol Et2O, THF; insol hydrocarbons.

Form Supplied in: solutions of PhMgBr in Et2O and THF and of PhMgCl in THF and THF/toluene are commercially available.

Analysis of Reagent Purity: see Methylmagnesium Bromide.

Preparative Methods: in spite of their commercial availability, solutions of PhMgBr8 and PhMgCl9 are frequently prepared from reaction of a phenyl halide and Mg, usually in Et2O or THF.1c,e,7 Preparation of PhMgBr in Et2O is routine, but the formation of PhMgCl from PhCl and magnesium is difficult to initiate and sustain. By contrast, preparation is generally successful in THF.9 Use of activated10 Magnesium makes possible otherwise difficult preparations, allows the use of lower temperatures which may minimize undesired reactions with other functional groups in the reagent, and allows the use of Et2O, other less favorable ethers, and hydrocarbons. Stirring Mg under nitrogen is one activation procedure;11 other effective procedures (chemical treatment of the Mg,12 preparation of Mg by reduction of salts,13 use of ethylene bromide as a coreagent during the preparation14) can introduce other species.

Handling, Storage, and Precautions: see Methylmagnesium Bromide. Phenyl Grignard reagents do not significantly attack Et2O or THF at normal reaction temperatures.

Representative Applications.1b-f

See also Methylmagnesium Bromide. Phenyl Grignard reagents are used most frequently in reactions that result in attachment of the organic group to an electrophilic carbon atom of the substrate, most often of a carbonyl group, nitrile, or other unsaturated function. The oxazoline function, easily transformed into other functions, facilitates displacement of a methoxyl group (eq 1), probably both by its electronic effects and by coordinating with the Grignard reagent.15

Related Reagents.

Phenyllithium.


1. (a) Lindsell, W. E. In Comprehensive Organometallic Chemistry; Wilkinson, G.; Stone, F. G. A.; Abel, E. W., Eds.; Pergamon: Oxford, 1982; Chapter 4. (b) Wakefield, B. J. In Comprehensive Organometallic Chemistry; Wilkinson G.; Stone, F. G. A.; Abel, E. W., Eds.; Pergamon: Oxford, 1982; Chapter 44. (c) Nützel, K. MOC 1973, 13/2a, 47. (d) Raston, C. L.; Salem, G. In The Chemistry of the Metal-Carbon Bond; Hartley, F. R., Ed.; Wiley: Chichester, 1987; Vol. 4, Chapter 2. (e) Old but still extremely useful is: Kharasch, M.; Reinmuth, O. Grignard Reactions of Nonmetallic Substances; Prentice-Hall: New York, 1954. (f) Ioffe, S. T.; Nesmeyanov, A. N. The Organic Compounds of Magnesium, Beryllium, Calcium, Strontium and Barium; North-Holland: Amsterdam, 1967.
2. Evans, D. F.; Fazakerley, G. V. JCS(A) 1971, 184.
3. Smith, M. B.; Becker, W. E. T 1966, 22, 3027; Smith, M. B.; Becker, W. E. T 1967, 23, 4215.
4. Walker, F. W.; Ashby, E. C. JACS 1969, 91, 3845.
5. Stucky, G.; Rundle, R. E. JACS 1964, 86, 4825.
6. Schröder, F. A. CB 1969, 102, 2035.
7. Bickelhaupt, F. In Inorganic Reactions and Methods; Hagen, A. P., Ed.; VCH: New York, 1989; Vol. 10, Section 5.4.2.2.1; FF 1967, 1, 415.
8. Allen, C. F. H.; Converse, S. OSC 1941, 1, 226; Hiers, G. S. OSC 1941, 1, 550.
9. Ramsden, H. E.; Balint, A. E.; Whitford, W. R.; Walburn, J. J.; Cserr, R. JOC 1957, 22, 1202.
10. Reviews: Ref. 7; Lai, Y.-H. S 1981, 585.
11. Baker, K. V.; Brown, J. M.; Hughes, N.; Skarnulis, A. J.; Sexton, A. JOC 1991, 56, 698.
12. Oppolzer, W.; Schneider, P. TL 1984, 25, 3305; Oppolzer, W.; Cunningham, A. F. TL 1986, 27, 5467; Bönnemann, H.; Bogdanović, B.; Brinkmann, R.; He, D.-W.; Spliethoff, B. AG(E) 1983, 22, 728. Also see Bartmann, E.; Bogdanović, B.; Janke, N.; Liao, S.; Schlichte, K.; Spliethoff, B.; Treber, J.; Westeppe, U.; Wilczok, U. CB 1990, 123, 1517.
13. Rieke, R. D.; Bales, S. E. JACS 1974, 96, 1775. Rieke, R. D.; Bales, S. E.; Hudnall, P. M.; Burns, T. P.; Poindexter, G. S. OSC 1988, 6, 845 (note particularly footnote 19).
14. Pearson, D. E.; Cowan, D.; Beckler, J. D. JOC 1959, 24, 504.
15. Gant, T. G.; Meyers, A. I. JACS 1992, 114, 1010.

Herman G. Richey, Jr.

The Pennsylvania State University, University Park, PA, USA



Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.