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


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).

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Original Publication URL: http://dx.doi.org/10.1039/b605458g

Description/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.

Item Type: Article
ISSNs: 1477-0520 (print)
Related URLs:
Subjects: Q Science
Q Science > QD Chemistry
Divisions: University Structure - Pre August 2011 > School of Chemistry
ePrint ID: 44491
Date Deposited: 06 Mar 2007
Last Modified: 27 Mar 2014 18:29
URI: http://eprints.soton.ac.uk/id/eprint/44491

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