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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

Lory, Pedro M.J.; Jones, Raymond C.F.; Iley, James N.; Coles, Simon J. and Hursthouse, Michael 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 and Biomolecular Chemistry, 4 pp. 3155–3165.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1039/b605458g
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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: Journal Article
ISSN: 1477-0520
Extra Information: Some of the symbols may not have transferred correctly into this bibliographic record and/or abstract.
Keywords: intramolecular; 1,3-dipolar cycloaddition; dihydroimidazolium ylides; imidazoline ylides;
Academic Unit/Department: Science > Life, Health and Chemical Sciences
Item ID: 5954
Depositing User: James Iley
Date Deposited: 29 Nov 2006
Last Modified: 02 Dec 2010 19:55
URI: http://oro.open.ac.uk/id/eprint/5954
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