Synthesis of Regioisomeric Pyrido[c]azocanones from Azaindanone Derivatives

Abstract

A ring enlargement reaction with methylamine gave new pyrido[2,3‐c]‐, pyrido[3,4‐c]‐ and pyrido[3,2‐c]azocanone derivatives from cyclic β‐oxo esters with a cyclopentapyridine skeleton and a 1,4‐diketone moiety. The starting materials for this ring transformation were either prepared from halogenopyridine carboxylates by Heck reaction and subsequent hydrogenation, or (halogenomethyl)pyridine carboxylates were submitted to SN reaction with diethyl malonate. Both routes were completed by Dieckmann condensation to build the cyclic β‐oxo ester structure and alkylation with phenacylbromide to install the 1,4‐diketone motif.

Recent Advances in the Synthesis of Hydrogenated Azocine-Containing­ Molecules

“…A bismuth-free strategy of ring enlargement was also successful in the case of regioisomeric pyrido[ c ]azocines. 4 Synthesized from commercially available materials, three cyclopentapyridine derivatives 3 , 6 , and 9 , containing β-oxo ester moieties, were alkylated with phenacyl bromide to give 1,4-diketones 4 , 7 , and 10 . The latter were subjected to ring-expansion reactions with methylamine giving pyrido[2,3- c ]azocine 5 (Scheme 2 ), pyrido[3,4- c ]azocine 8 (Scheme 3 ), and pyrido[3,2- c ]azocine 11 (Scheme 4 ) in 36–64% yield.…”

Synthesis of Benzo[b]azocin‐2‐ones by Aryl Amination and Ring‐Expansion of α‐(Iodophenyl)‐β‐oxoesters

“…This transformation was then applied to pyrrolidine 6 and tetrahydrothiophene derivatives 7 to furnish diazocanes 10 and thiazocanes 11 . Furthermore, benzo‐ (products 12 ), pyrido‐ (products 13 and two regioisomers) and thienoannulated congeners 14 (and two regioisomers) were prepared.…”

Construction of Polycyclic β-Ketoesters Using a Homoconjugate Addition/Decarboxylative Dieckmann Annulation Strategy

“…Finally, heterocyclic scaffolds were also evaluated. Cyclization to the indanone scaffold in 22 proceeded efficiently in 90% yield. Pyridines, indoles, and benzothiophenes could all be incorporated into cyclization products, but pyridine 4p was isolated in relatively low yield and carbazole 23 was formed as a result of facile air oxidation during handling and isolation.…”