1) The Brook rearrangement is an intramolecular rearrangement involving the 1,2-migration of a silyl group from carbon to oxygen under basic conditions. 2) The reaction proceeds through a pentacoordinate silicon intermediate and involves the migration of an alpha-silyloxyanion to an alpha-silylcarbanion. 3) The Brook rearrangement has various synthetic applications, including the stereoselective construction of 8-membered carbocycles and the synthesis of natural products like cyanthins and onocerin.

1. BY
Dr. Gurumeet.C.Wadhawa
DEPARTMENT OF CHEMISTRY
K. B. P. College,Vashi,Navimumbai
Brook Rearrangement

2. BROOK
REARRANGEMENT

3. INTRODUCTION
Discovered by Canadian Chemist
Adrian Gibbs Brook in 1958.
Also known
rearrangement
migration.
as [1,2]-Brook
or [1,2]-Silyl
Intramolecular rearrangement.
2

4. DEFINITION
 The 1,2- migration of a silyl group from carbon to
oxygen under basic conditions is known as Brook
rearrangement.
 Rearrangement of α-silyloxyanion to α-
silylcarbanions involving a pentacoordinate
siliconintermediate. 3

5. Alpha-silyl
oxyanion
Pentacoordinate
siliconintermediate
Alpha-silyl
carbanion
Silyl ether or
Oxysilane
5

6. REACTION
6

7. 1)In the late 1950s, A.G. Brook observed the intramolecular anionic
migration of silyl groups from a carbon to an oxygen atom.
2)1,2 This migratory aptitude of the silyl group was later found to be more
general. Therefore, all the [1,n]- carbon to oxygen silyl migrations are
referred to as Brook rearrangements.
3)The reaction is based on the great susceptibility of silicon toward a
nucleophilic attack and the formation of a strong silicon-oxygen bond (Si-
O) from the relatively weak silicon-carbon bond.
4)The reverse process is called the retro-Brook rearrangement and was
first reported by J.L. Speier.

8. MECHANISM
8

13. CHARACTERISTICS
 The rate of reaction depends on the amount of
added base, but this was not consumed and was
used in substoichiometric amounts. So the
reaction follows Pseudofirst order kinetics.
 A silyl shift from oxygen to carbon, the reverse
process is called retro-Brook rearrangement. 8

14. •[1,2]-silyl migration is a equilibrium process.
•Aza- or Thia- variants of the rearrangement
involving silyl shifts from carbon to nitrogen or
sulphur respectively, have also been observed.
14

15. SYNTHETICAPPLICATIONS
15
APPLICATION 1:
 K. Takeda and co-workers synthesized the tricyclic core
of the cyanthins using a Brook rearragement mediated-
reaction.

16. APPLICATION 2:
 K. Takeda developed a new synthetic strategy for the
stereoselective construction of 8 membered
carbocycles utilizing a Brook rearrangement.
16

17. APPLICATION 3:
 E.J. Corey synthesized (+)- Onocerin from farnesyl
acetate- derived acyl silane via four-component
coupling and tetracyclization steps.
17

18. REFERENCE
18
 JiebJack Li:Name Reactions Third Edition;Springer
Science & Bussiness Media, 2006:Page no:83-84
 Laszlo Kurti,Barbara Czako:Strategic Applications of
Named Reactions in Organic Synthesis;Elsevier,29-
Apr-2005;page no:64-65
 Christian M. Rojas:Molecular Rearrangements in
Organic Synthesis:Wiley,March-2015,Page no:207-241

19. A. Hassner, I.Namboothiri;Organic Syntheses Based
on Named Reactions, Third Edition;Elsevier;Page no:62
Michiko Sasaki, Kei Takeda:Brook rearrangement:
Wiley Online library:2-Oct-2015:Chapter 6
TutorVista.com
19

20. References
1. Brook, A. G. J. Am. Chem. Soc. 1958, 80, 1886-1889. Adrian G.
Brook (1924) was born in Toronto, Canada. He was a professor in
Lash Miller Chemical Laboratories, University of Toronto, Canada.
2. Brook, A. G. Acc. Chem. Res. 1974, 7, 77-84. (Review).
3. Bulman Page, P. C.; Klair, S. S.; Rosenthal, S. Chem. Soc. Rev.
1990, 19, 147-195. Review).
4. Fleming, I.; Ghosh, U. J. Chem. Soc., Perkin Trans. 1 1994, 257-
262.
5. Moser, W. H. Tetrahedron 2001, 57, 2065-2084. (Review).
6. Okugawa, S.; Takeda, K. Org. Lett. 2004, 6, 2973-2975.
7. Matsumoto, T.; Masu, H.; Yamaguchi, K.; Takeda, K. Org. Lett.
2004, 6, 4367 4369.
8. Clayden, J.; Watson, D. W.; Chambers, M. Tetrahedron 2005, 61,
3195-3203.
9. Smith, A. B., III; Xian, M.; Kim, W.-S.; Kim, D.-S. J. Am. Chem.
Soc. 2006, 128,
12368–12369.
10. Mori, Y.; Futamura, Y.; Horisaki, K. Angew. Chem. Int. Ed. 2008,
47, 1091–1093.
11. Greszler, S. N.; Johnson, J. S. Org. Lett. 2009, 11, 827–830.
12. He, Y.; Hu, H.; Xie, X.; She, X. Tetrahedron 2013, 69, 559-563.

21. THANKYOU...
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