Brook rearrangement

It is an intramolecular rearrangement reaction in which the 1,2-migration of silyl group from carbon to oxygen under basic conditions.It involves the formation of a pentacoordinate siliconintermediate.Discovered by Adrian Gibbs Brook in 1958.

1. BROOK REARRANGEMENT PREPARED BY ANUSREE V 1 ST SEMESTER MPHARM PHARMACEUTICAL CHEMISTRY AL SHIFA COLLEGE OF PHARMACY

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

3. 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

4. 4

5. REACTION 5

6. METHODS FOR GENERATION OF α -SILYL ALKOXIDES 6

7. MECHANISM 7

8. 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

9. [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. 9

10. SYNTHETIC APPLICATIONS K. Takeda and co-workers synthesized the tricyclic core of the cyanthins using a Brook rearragement mediated-reaction. APPLICATION 1: 10

11. APPLICATION 2: K. Takeda developed a new synthetic strategy for the stereoselective construction of 8 membered carbocycles utilizing a Brook rearrangement. 11

12. APPLICATION 3: E.J. Corey synthesized (+)- Onocerin from farnesyl acetate- derived acyl silane via four-component coupling and tetracyclization steps. 12

13. reference 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 13

14. 14 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

15. THANK YOU... 15