A-Pyrone derivatives

Synthesis, structure, and transformations of a-pyrone derivatives, viz., xanthy-rones, glaucyrones, and chelated magnesium enolates 98T8243. 

In spite of these first successful results, so far Stille cross-couplings have rarely reported employing functionalized stannylated allenes such as easily available donor-substituted allene 80a or allenyl esters such as 81 (Scheme 14.19) [19, 41, 42]. A single palladium-catalyzed annulation reaction with 80b as precursor leading to an a-pyrone derivative was reported [43],... 

Kraut, L. et al., Carboxylated a-pyrone derivatives and flavonoids from the liverwort Dumortiera hirsuta. Phytochemistry, 42, 1693, 1996. 

Schenck and Steinmetz346 described an example which can be mentioned here. An a-pyrone derivative was obtained by a photochemical reaction of furan with diazoacetic ester ... 

Diels-Alder reactions. Adducts of high ee are obtainable from the condensation of a-pyrone derivatives with enol ethers catalyzed by Ti-BINOLate. ... 

Altemaria, one of the most common moulds contaminating foods and feeds, produces many metabolites with different chemical structures. Two metabolites of m or concern because of their toxicity and/or natural occurrence in a number of fungal contaminated commodities are the dibenzo-a-pyrone derivatives altomariol (AOH) and altenuisol (ATS). 

A remarkable synthesis of the heavily substituted 4-quinolizones 45 and 46, due to Van Allan and Reynolds,39 starts from the acyclic precursor 43, or from the a-pyrone derivative 44. 

Gogte synthesis. Formation of a-pyrone derivatives by rearrangement of acyl-substituted gluta-conic anhydrides. 

Reactions of substituted bis(3-aIkoxybenzoyl) peroxides in neat phenols afford mainly 8-alkoxy-677-dibenzo[fc, d]pyran-6-ones and orf/zo-benzoyloxylation products of the phenol. For example, bis(3,4-dimethoxybenzoyl) peroxide (561) in neat p-methylphenol was completely decomposed in 1 h at 60 °C with the formation of a dibenzo-a-pyrone derivative 562 (60%) together with an ortho-ortho coupled product 563 (21%) and benzoate 564 (5%). In contrast, dibenzoyl peroxides having no mefa-electron-releasing substituents gave mainly ort/zo-benzoyloxyphenols. For example, decomposition of bis(4-methoxybenzoyl)... 

The reaction of 4-amino-1,2,4-triazole with a-pyrone derivatives 286 and leads to N-triazolylpyridones 288 and 289 [09CB1990 85JCS(P1)12O9]. However, it was not possible to obtain such compounds using 1-aminopy-... 

Heating compound 101 with diethylamine yields a mixture of two products, one of which is a pyrone derivative (99MC671) (Scheme 114). 

Pyrimidines la 266,438,439 lb 32,430 Pyrimidine nucleoside derivatives lb 290 Pyrocatechol lb 170,172,185 -, 4-rerr-butyl- lb 201 Pyrocatechol derivatives lb 119 Pyrocatechol violet reagent la 398 Pyrogallol lb 383,399,400 Pyrogallol derivatives lb 312 Pyrolysis of organic substances la 92,96 a-Pyrone derivatives la 288 lb 387,388 Pyrrole lb 268,270 Pyrrole alkaloids la 66 lb 279 Pyrrole derivatives la 266.269,270 lb 63 Pyrrolidine derivatives lb 290 Pynolizidine alkaloids lb 243,246,291... 

Drewes, S.E., B.M. Sehlapelo, M.M. Horn, R. Scott-Shaw, and P. Sandor 5,6-Dihydro-a-pyrones and Two Bicyclic Tetrahydro-a-pyrone Derivatives from Crypto-carya latifolia. Phytochem., 38, 1427 (1995). 

Two other a,P-unsaturated 5-lactones (50) and (51), substituted in position 3, were identified in the flavor of Burley tobacco 111). 3-Iso-propyl-2-penten-5-olide (51) and its saturated derivative (52) impart a coconut-like note (555) to tobacco 111). Two doubly unsaturated 5-lactones were identified in peach flavor 567, 568). These are 2,4-pentadien-5-olide (or oc-pyrone) (53) and 2,4-decadien-5-olide (54). The latter, which was also identified in mushrooms 89) has a powerful buttery note. Detailed descriptions of the odors of a-pyrone derivatives are to be found in the literature 476). 

PiTTET, O., and E. M. Klaiber Synthesis and Flavor Properties of Some Alkyl-Substituted a-Pyrone Derivatives. J. Agric. Food Chem. 23, 1189 (1975). 

Cyclopropanation of coumarin derivatives 11 to form fused cyclopropyl cyclopen-tanones 12 via domino carbon-carbon bond formation, ring opening, and bicycle formation was performed in the presence of dimethylsulfoxonium methylide (Scheme 5.5) [19]. To ensure good reaction outcomes, this skeleton transformation reaction operates in the presence of a-pyrone derivatives 11, which bear a methyl ester moiety as the electron-withdrawing group at the C3 position. 

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