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Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de] quinoxalines and imidazo[1,2-a]indoles

Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de] quinoxalines and imidazo[1,2-a]indoles
Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de] quinoxalines and imidazo[1,2-a]indoles
N-Alkylation of 4,5-dihydroimidazoles with alkene-containing bromomethyl ketones and treatment of the so-formed 4,5-dihydroimidazolium ions with DBU gives rise to an intramolecular 1,3-dipolar cycloaddition reaction that affords ( via a reaction cascade involving eliminative ring-opening, recyclisation and prototropic tautomerism) unexpected hexahydropyrrolo[1,2,3-de] quinoxaline products. Steric bulk in both the dihydroimidazole and the dipolarophile allows isolation of an imidazo[ 1,2-a] indole, the initial product of cycloaddition. When the bromomethyl ketone contains no other functionality, or when cycloaddition is inhibited due to steric constraints, the dihydroimidazolium ion undergoes ring-opening hydrolysis followed by recyclization of the exposed amino ketone to afford either 3-alkyl-1-formylpiperazine-2-ones or 3-aryl-1-formyl-1,4,5,6-tetrahydropyrazines.
1477-0520
3155-3165
Lory, P.M.J.
69bebd61-5c7b-4ff5-aa71-86707ee440e8
Jones, R.C.F.
bae255f0-9438-4ed8-bcd2-82f3c7537073
Iley, J.N.
6006c3c3-4478-4b0f-a6a5-44b7e5e1df1e
Coles, S.J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hursthouse, M.B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Lory, P.M.J.
69bebd61-5c7b-4ff5-aa71-86707ee440e8
Jones, R.C.F.
bae255f0-9438-4ed8-bcd2-82f3c7537073
Iley, J.N.
6006c3c3-4478-4b0f-a6a5-44b7e5e1df1e
Coles, S.J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hursthouse, M.B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da

Lory, P.M.J., Jones, R.C.F., Iley, J.N., Coles, S.J. and Hursthouse, M.B. (2006) Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de] quinoxalines and imidazo[1,2-a]indoles. Organic & Biomolecular Chemistry, 4 (16), 3155-3165. (doi:10.1039/b605458g).

Record type: Article

Abstract

N-Alkylation of 4,5-dihydroimidazoles with alkene-containing bromomethyl ketones and treatment of the so-formed 4,5-dihydroimidazolium ions with DBU gives rise to an intramolecular 1,3-dipolar cycloaddition reaction that affords ( via a reaction cascade involving eliminative ring-opening, recyclisation and prototropic tautomerism) unexpected hexahydropyrrolo[1,2,3-de] quinoxaline products. Steric bulk in both the dihydroimidazole and the dipolarophile allows isolation of an imidazo[ 1,2-a] indole, the initial product of cycloaddition. When the bromomethyl ketone contains no other functionality, or when cycloaddition is inhibited due to steric constraints, the dihydroimidazolium ion undergoes ring-opening hydrolysis followed by recyclization of the exposed amino ketone to afford either 3-alkyl-1-formylpiperazine-2-ones or 3-aryl-1-formyl-1,4,5,6-tetrahydropyrazines.

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Published date: 2006

Identifiers

Local EPrints ID: 44491
URI: http://eprints.soton.ac.uk/id/eprint/44491
ISSN: 1477-0520
PURE UUID: c4921db0-4ffd-44b8-8082-17550d0461d9
ORCID for S.J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

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Date deposited: 06 Mar 2007
Last modified: 16 Mar 2024 03:05

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Contributors

Author: P.M.J. Lory
Author: R.C.F. Jones
Author: J.N. Iley
Author: S.J. Coles ORCID iD
Author: M.B. Hursthouse

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