2-Pyridinone esters

Computer-Aided Library Design for Agrochemical Lead Generation Design and Synthesis of Ring-Fused 2-Pyridinone Esters... 

Table I. Herbicide Property Ranges for Commercial Products and the Ring-Fused 2-Pyridinone Ester Library...

In a typical reaction, a series of C - O linked pyrazinone-triazoles were irradiated with an excess (3.5 equiv) of DMAD in o-DCB. The reactions were completed in 6-20 min at 180 °C, using a maximum irradiation power of 200 W. After spontaneous elimination of the corresponding isocyanate or cyanogen chloride, the pyridines and pyridinones were formed in combined yields of 71-99%. It is noteworthy that the pyrazinones with an aryl moiety at the N-1 position yielded pyridines as major products, while those with ben-zyUc or alkyl ester moieties at the N-1 position furnished the corresponding pyridinones as major products. 

In Scheme 6.230, the multistep synthesis of 2,3-dihydro-4-pyridones is highlighted [411]. The pathway described by Panunzio and coworkers starts from a dioxin-4-one precursor, which is readed with 2 equivalents of benzyl alcohol under solvent-free microwave conditions to furnish the corresponding /1-diketo benzyl esters. Subsequent treatment with 1 equivalent of N,N-dimethylformamide dimethyl acetal (DMFDMA), again under solvent-free conditions, produces an enamine, which is then cyclized with an amine building block (1.1 equivalents) to produce the desired 4-pyridinone produds. All microwave protocols were conducted under open-vessel conditions using power control. 

Other reports also demonstrate the efficiency of this reaction for the synthesis of pyrrolidine prostacyclin analogues [183], ( )-indolizidine 209B [184], pyridinones [185] and pyrrolidine-2-ylidene esters [186], though in one case the structure of the substrate had to be modified to avoid an undesired reaction [187]. 

Keto esters and amides are versatile intermediates in organic synthesis and often are prepared from acyl Meldrum s acid adducts. This method involves formation of acyl Meldrum s adducts by reaction of Meldrum s acid with activated carboxylic acids followed by decarboxylation in the presence of nucleophiles such as alcohols or amines (Scheme 21.2). The ability of readily available acyl Meldrum s acids to react with various nucleophiles allows quick access to a variety of functionalized compounds. Apphcation of this methodology in synthetic chemistry has been widely exploited. For example, acyl Meldrum s adducts can react with imines to prepare pyridinones or... 

The synthesis of optically active thiazolo[3,2-fl]pyridinones has been described. Chiral thiazolines 27, prepared from the condensation of imino ethers 25 with (R)-cysteine methyl ester 26, undergo a ketene-imine cycloaddition reaction with Meldrum s acid derivatives 28 to give thiazolo[3,2-a]pyridinones 29 in good yields <01JOC6756>. 

Hayashi has reported a wide range of reactions employing rhodium with chiral binaphthylphosphine ligands, for example in the asymmetric 1,4-addition of boronic acids and triarylboranes to various unsaturated starting materials a,p-unsaturated ketones, esters, 1-alkenylphosphonates, nitroalkenes and 5,6-dihydro-2(lH)-pyridinones. ... 

Barluenga unexpectedly obtained 3-pyrrolin-2-ones (instead of the corresponding pyridinones) in a reaction involving diethyl fumarate (280) (Scheme 69 1981S200). Treatment of 280 with imine 279 in the presence of AICI3 gives the 3-pyrrolin-2-one 281 (Scheme 69 1981S200). The structure of 281 was confirmed by NMR analysis of its LiAlHa reduction product. Mechanistically, the transformation proceeds via a Michael addition by the enamine tautomer of 279 to the unsaturated ester 280 followed by an intramolecular amidation. 

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