Synthesis of novel polycarbonyl Schiff bases by ring-opening reaction of ethyl 5-acyl-4-pyrone-2-carboxylates with primary mono- and diamines

Abstract

An approach for the introduction of the tricarbonyl moiety into various amines has been developed based on acylpyrones.

The Construction of Polycyclic Pyridones via Ring-Opening Transformations of 3-hydroxy-3,4-dihydropyrido[2,1-c][1,4]oxazine-1,8-diones

“…We started with the ANRORC reaction of 5-acyl-4-pyrone-2-carboxylate 1 with 2,2-dimethoxyethylamine as the effective method for the preparation of 4-pyridones [ 3 , 17 , 28 , 29 ] ( Scheme 2 , Table 1 ). The ring-opening transformations proceeded under reflux in toluene for 4 h to produce pyridones 2a–d,f in 30–90% yields.…”

Synthesis of 5-Aroyl-2-aryl-3-hydroxypyridin-4(1H)-ones

“…Additionally, no reaction appeared when pyrones 1 were refluxed in an ethanolic solution of ammonium chloride. The reaction mechanism includes the attack of the ammonia molecule at the C-6 position, followed by the pyrone ring opening and intramolecular cyclization [21].…”

“…Additionally, no reaction appeared when pyrones 1 were refluxed in an ethanolic solution of ammonium chloride. The reaction mechanism includes the attack of the ammonia molecule at the C-6 position, followed by the pyrone ring opening and intramolecular cyclization [21]. The debenzylation of products 2a-c under the action of TMSI generated in situ in anhydrous acetonitrile from TMSCl and NaI allowed us to obtain 5-acyl-2-hetaryl substituted 3,4-HPOs 3a-c in 89-92% yields.…”

2-Aryl-6-Polyfluoroalkyl-4-Pyrones as Promising RF-Building-Blocks: Synthesis and Application for Construction of Fluorinated Azaheterocycles

“…4-Pyrone unit is an important heterocyclic motif, which is frequently present in numerous natural products that exhibit a wide range of important biological activities [ 1 , 2 , 3 , 4 , 5 ] and medicines, such as phenoxan [ 5 ] ( Figure 1 ). Mainly, pyrones are of interest as useful and versatile building-blocks for the synthesis of valuable molecules [ 6 , 7 , 8 , 9 ], including pharmaceuticals [ 10 ] and pyranic fluorophores [ 11 ]. Pyrones as polyelectrophilic substrates and cyclic enone are able to react regioselectively with nucleophiles to undergo ring-opening transformations affording azaheterocycles [ 12 , 13 , 14 , 15 , 16 ].…”