Synthesis of substituted 1,2,3,4-tetrahydroquinolines
Synthesis of substituted 1,2,3,4-tetrahydroquinolines
This thesis generalises the earlier reported one pot synthesis of 1,2,3,4-tetrahydroquinoline derivatives formed in formal [4+ 2] cycloadditions of aromatic iminium ions, which behave as 2-azadiene equivalents, with electron rich alkenes including cyclopentadiene, styrenes and 3,4-dihydro-2H -pyran. The iminium ions, derived from a series of aromatic amines (aniline derivatives; 5-, 7- and 8-aminoquinolines; 5-aminoisoquinoline; 1,4-di and 1-aminoanthraquinones and 3,6-diaminoacridine) and aqueous formaldehyde with trifluoroacetic acid catalysis, led to a number of novel azaheterocycles each possessing a 1,2,3,4-tetrahydroquinoline nucleus, including three compounds possessing an 11-azasteroidal skeleton from reactions with cyclopentadiene.
3-Aminopyridine gave rise to [1,5]naphthyridine derivatives in an analogous fashion. Most reactions proceeded in good to excellent yields. The introduction includes a thorough review of the literature concerning related aromatic 2-azadienes, their reactions being viewed as examples of aza Diels-Alder cycloadditions.
Hence an overview of the aza Diels-Alder reaction as a ring-forming synthetic strategy is presented, focusing on applications to heterocyclic synthesis. Consideration is given to the mechanism of the reactions and a non-concerted mechanism is proposed, as evidenced by the isolation of intermediate γ-aminoalcohols (which can be cyclised to the 1,2,3,4-tetrahydroquinoline derivatives under the reaction conditions) and by the observation of side products including 1,3-oxazines, which arise from trapping of an intermediate carbocation.
Successful cyclisations of 3,6-diaminoacridine and o-phenylenediamine with cyclopentadiene and of 1,4-diaminoanthraquinone with styrene indicate the power of this approach for the easy and rapid synthesis of chiral diamines of potential importance in asymmetric synthesis. 2-Aminopyridine derivatives behaved instead as 1,3-diazadienes with cyclopentadiene and styrenes giving rise to pyrido[1,2-a]pyrimidine derivatives.
University of Southampton
1993
Merriman, Glynn David
(1993)
Synthesis of substituted 1,2,3,4-tetrahydroquinolines.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis generalises the earlier reported one pot synthesis of 1,2,3,4-tetrahydroquinoline derivatives formed in formal [4+ 2] cycloadditions of aromatic iminium ions, which behave as 2-azadiene equivalents, with electron rich alkenes including cyclopentadiene, styrenes and 3,4-dihydro-2H -pyran. The iminium ions, derived from a series of aromatic amines (aniline derivatives; 5-, 7- and 8-aminoquinolines; 5-aminoisoquinoline; 1,4-di and 1-aminoanthraquinones and 3,6-diaminoacridine) and aqueous formaldehyde with trifluoroacetic acid catalysis, led to a number of novel azaheterocycles each possessing a 1,2,3,4-tetrahydroquinoline nucleus, including three compounds possessing an 11-azasteroidal skeleton from reactions with cyclopentadiene.
3-Aminopyridine gave rise to [1,5]naphthyridine derivatives in an analogous fashion. Most reactions proceeded in good to excellent yields. The introduction includes a thorough review of the literature concerning related aromatic 2-azadienes, their reactions being viewed as examples of aza Diels-Alder cycloadditions.
Hence an overview of the aza Diels-Alder reaction as a ring-forming synthetic strategy is presented, focusing on applications to heterocyclic synthesis. Consideration is given to the mechanism of the reactions and a non-concerted mechanism is proposed, as evidenced by the isolation of intermediate γ-aminoalcohols (which can be cyclised to the 1,2,3,4-tetrahydroquinoline derivatives under the reaction conditions) and by the observation of side products including 1,3-oxazines, which arise from trapping of an intermediate carbocation.
Successful cyclisations of 3,6-diaminoacridine and o-phenylenediamine with cyclopentadiene and of 1,4-diaminoanthraquinone with styrene indicate the power of this approach for the easy and rapid synthesis of chiral diamines of potential importance in asymmetric synthesis. 2-Aminopyridine derivatives behaved instead as 1,3-diazadienes with cyclopentadiene and styrenes giving rise to pyrido[1,2-a]pyrimidine derivatives.
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Published date: 1993
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Local EPrints ID: 462415
URI: http://eprints.soton.ac.uk/id/eprint/462415
PURE UUID: 659ce114-7c59-47a9-8176-e52a8292e3ed
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Date deposited: 04 Jul 2022 19:07
Last modified: 04 Jul 2022 19:07
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Author:
Glynn David Merriman
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