Ring-fused pyridones

The use of microwave irradiation for this reaction, compared to conventional thermal heating, was investigated. Chloroform used as solvent under the conventional heating did only allow a temperature of 60 °C and a direct comparison between the two methods is therefore somewhat unfair imder these circumstances. Nevertheless, the microwave-assisted method is attractive and proved useful for both primary and secondary amines resulting in highly substituted pyrazolo ring-fused pyridones 40 in 68-86% yields within only 10 min. 

FVP of the aminomethylene derivatives of Meldrum s acid has been widely exploited as a route to ring-fused pyridones. The simple aryl derivatives 326 give quinolones 327 in moderate-to-excellent yields (Scheme 65 2009SL1847) although there can be some complications, such as... 

Fig. 11 A tentative mechanism for the reagent-free decarboxylation of ring-fused 2-pyridones obtained under MAOS conditions...

Pemberton N, Chorell E, Almqvist F (2006) Microwave-Assisted Synthesis and Functionalization of 2-Pyridones, 2-Quinolones and Other Ring-Fused 2-Pyridones. T. 1-30... 

Keywords 2-Pyridone 2-quinolone Ring-fused 2-pyridone... 

Fig. 1 Heterocycles bearing a 2-pyridone moiety with wide range of medicinal applications. Amrinone WIN 40680 1 is a cardiotonic agent for the treatment of heart failure. ZAR-NESTRA 2 is a selective farnesyl protein inhibitor and NP048 3 is a pilicide with novel antibacterial properties. The 2-pyridones 4, 5 and 6 are schematic representations of the three categories of 2-pyridones that wiU be covered in this chapter i.e., substituted 2-pyridones 4, 2-quinolones 5 and other ring-fused 2-pyridones 6...

Scheme 3 Examples of Dieckmann-type condensation (a) and [2 + 2 + 2] cycloaddition (b) leading to functionalized and ring-fused 2-pyridones...

Microwave-Assisted Synthesis of Ring-Fused /V-Substituted 2-Pyridones... 

Ring-fused 2-pyridone structures where the additional ring is fused over the nitrogen will be covered in this section. Other ring-fused systems can be obtained simply by using suitable cychc starting materials or by conducting intramolecular reactions, examples for the preparation of such systems can be found in the papers discussed in Sect. 2.2 [42,43]. 

This method has been extended to include imines other than A -thia-zolines, hence enabling the synthesis of multi ring-fused 2-pyridones (28,30, and 33, Scheme 8). Thus, by reacting dihydroisoquinoUnes 27 or /1-carboUnes 29 with acyl Meldrum s acid derivatives 24, a set of new ring-fused heterocycles was prepared in moderate to excellent yields (a and b. Scheme 8). These systems were prepared by using trifluoro acetic acid (TFA) as a proton source instead of solutions saturated with HCl (g). The switch of acid proved to be advantageous since it reduced the formation of by-products and increased the isolated yields. From a practical point of view, TFA is also su-... 

Scheme 9 Synthesis of ring-fused 2-pyridones via aminopropenoates using both solution-phase and solid-phase conditions...

Pemberton N, Chorell E, Almqvist F (2006) Microwave-Assisted Synthesis and Functionalization of 2-Pyridones, 2-Quinolones and Other Ring-Fused 2-Pyridones. 1 1-30 Ponnuswamy MN, Gromiha MM, Sony SMM, Saraboji K (2006) Conformational Aspects and Interaction Studies of Heterocyclic Drugs. 3 81-147 Prabhakar YS, Solomon VR, Gupta MK, Katti SB (2006) QSAR Studies on Thiazolidines A Biologically Privileged Scaffold. 4 161-248... 

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