Brominated isoindolines: Precursors to functionalised nitroxides
Micallef, Aaron S., Bott, Raymond C., Bottle, Steven E., Smith, Graham, White, Jonathon M. , Matsuda, Kenji, & Iwamura, Hiizu (1999) Brominated isoindolines: Precursors to functionalised nitroxides. Journal of the Chemical Society, Perkin 2, pp. 65-72.
A new, convenient method for the preparation of functionalised precursors to stable tetraalkylisoindoline nitroxides (aminoxyls) is presented. Simple treatment of 2-benzyl-1,1,3,3-tetramethylisoindoline 2 with Br2 in CCl4 gives rapid oxidative debenzylation, generating benzaldehyde and an unusual bromamine, 2-bromo-1,1,3,3-tetramethylisoindoline 4, in high yield. Treatment of the bromamine 4 with FeSO4 / H2SO4 results in bromination of the aromatic ring in varying yield, while rapid treatment with peroxide / tungstate causes debromination, generating 1,1,3,3-tetramethylisoindoline 3. Bromination of the isoindoline aromatic ring is more readily afforded by treatment of 2-benzyl-1,1,3,3-tetramethylisoindoline 2 with Br2 and AlCl3 in CCl4, producing 2,5-dibromo-1,1,3,3-tetramethylisoindoline 7 and/or 2,5,6-tribromo-1,1,3,3-tetramethylisoindoline 6 in varying yields depending upon the exact reaction conditions. Rapid treatment with peroxide / tungstate generates the corresponding bromine substituted isoindolines, 5-bromo-1,1,3,3-tetramethylisoindoline 5 and 5,6-dibromo-1,1,3,3-tetramethylisoindoline 8. Prolonged peroxide / tungstate treatment oxidises the substituted bromamines to the corresponding nitroxides, 5-bromo-1,1,3,3-tetramethylisoindolin-2-yloxyl 9 and 5,6-dibromo-1,1,3,3-tetramethylisoindolin-2-yloxyl 10. SQUID magnetic susceptibility measurements of crystalline 10 reveal strong antiferromagnetic interradical spin coupling. The crystal structures of 10, 2-bromo-1,1,3,3-tetramethylisoindoline 4 and the hydrobromide dihydrate salt of 1,1,3,3-tetramethylisoindoline 3 (3a) have also been determined, with 10 displaying an interesting molecular packing arrangement
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|Item Type:||Journal Article|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology|
|Copyright Owner:||Copyright 1999 Royal Society of Chemistry|
|Copyright Statement:||Reproduced by permission of The Royal Society of Chemistry, no further distribution permitted.|
|Deposited On:||18 Oct 2005|
|Last Modified:||11 Aug 2011 04:16|
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