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Synthesis of imidazo 1,2-a pyridines from unactivated 2-alkyl-4,5-dihydroimidazoles through conjugate N-addition

Synthesis of imidazo 1,2-a pyridines from unactivated 2-alkyl-4,5-dihydroimidazoles through conjugate N-addition
Synthesis of imidazo 1,2-a pyridines from unactivated 2-alkyl-4,5-dihydroimidazoles through conjugate N-addition
2-Alkyl-4,5-dihydroimidazoles undergo annulation with alpha,beta-unsaturated aldehydes and ketones via conjugate addition of the N-1 nitrogen atom and subsequent enamine-aldol condensation of C(alpha) to form imidazo[1,2-a]pyridines having reversed regiochemistry of annulation from that observed with a dihydroimidazole carrying an activating group at C(alpha); annulation with beta-ketoesters also affords imidazo[1,2-a]pyridines, but now with the same regiochemistry as found with a C(alpha)-activated dihydroimidazole and necessitating a revision of earlier reported structures. Dialkyl acetylenedicarboxylates undergo conjugate N-addition but act as 1,2- rather than 1,3-bis-electrophiles to form pyrrolo[1,2-a]imidazoles.
heterocyclic ketene aminals, 4, 5-dihydroimidazoles, imidazolines, alkylation, enones
2331-2342
Jones, R.C.F.
bae255f0-9438-4ed8-bcd2-82f3c7537073
Dimopoulos, P.
ad6c099d-9866-4f92-9d25-9ae0008cff55
Coles, S.C.
d3d38a6a-f12f-4e58-9cda-a1db6805f777
Light, M.E.
d04ad463-ba94-4c59-ab35-a64901f32501
Hursthouse, M.B.
427032bc-428c-4396-adb0-b38e87e908e7
Jones, R.C.F.
bae255f0-9438-4ed8-bcd2-82f3c7537073
Dimopoulos, P.
ad6c099d-9866-4f92-9d25-9ae0008cff55
Coles, S.C.
d3d38a6a-f12f-4e58-9cda-a1db6805f777
Light, M.E.
d04ad463-ba94-4c59-ab35-a64901f32501
Hursthouse, M.B.
427032bc-428c-4396-adb0-b38e87e908e7

Jones, R.C.F., Dimopoulos, P., Coles, S.C., Light, M.E. and Hursthouse, M.B. (2000) Synthesis of imidazo 1,2-a pyridines from unactivated 2-alkyl-4,5-dihydroimidazoles through conjugate N-addition. Journal of the Chemical Society, Perkin Transactions 1, (15), 2331-2342.

Record type: Article

Abstract

2-Alkyl-4,5-dihydroimidazoles undergo annulation with alpha,beta-unsaturated aldehydes and ketones via conjugate addition of the N-1 nitrogen atom and subsequent enamine-aldol condensation of C(alpha) to form imidazo[1,2-a]pyridines having reversed regiochemistry of annulation from that observed with a dihydroimidazole carrying an activating group at C(alpha); annulation with beta-ketoesters also affords imidazo[1,2-a]pyridines, but now with the same regiochemistry as found with a C(alpha)-activated dihydroimidazole and necessitating a revision of earlier reported structures. Dialkyl acetylenedicarboxylates undergo conjugate N-addition but act as 1,2- rather than 1,3-bis-electrophiles to form pyrrolo[1,2-a]imidazoles.

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More information

Published date: 2000
Keywords: heterocyclic ketene aminals, 4, 5-dihydroimidazoles, imidazolines, alkylation, enones

Identifiers

Local EPrints ID: 39126
URI: http://eprints.soton.ac.uk/id/eprint/39126
PURE UUID: b1ca6e99-c61c-44f7-9e50-50e82ffc6010

Catalogue record

Date deposited: 17 Jul 2006
Last modified: 15 Jul 2019 19:01

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