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Acylketene, generated from 2,2,6-trimethyl-4 H -1,3-dioxin-4-one reacts with aryl aldimines derived from 4-methyl-2-aminopyridine to give a variety of products, depending on the substituent on the C-aryl group, base used, and hydrolytic stability of the starting aldimine. Also the presence of the N -(2-pyridyl) group plays an important role in the fate of the reaction course, frequently participating in intramolecular conjugate additions, giving rise to interesting heterocycles.

A new method for a one-step synthesis of imidazolidin-4-ones is developed based on tandem nucleophilic additions-decarboxylation-intramolecular cyclizations of imines with a Leuchs′ anhydride.

The pyrrolidine-catalyzed reactions of benzalacetones (I) with cyclopentadiene leads to isolable intermediate Michael adducts (III) and (IV), which are converted into 1,2-dihydropentalenes (V) at longer reaction times.

The pyrrolidine-catalyzed condensation of carbonyl compounds with cyclopentadiene (I) proceeds readily for a wide diversity of aldehydes and ketones in methanol/water mixtures, affording the product fulvenes in reasonable yields simply by vacuum filtration.

A variety of 1,5-diarylpyrazol-3-propanoic acid derivatives is synthesized and evaluated as COX-1/2 and 5-LO-mediated LTB4 synthesis inhibitors.

1-Arylallenes react with singlet oxygen via 1,2-and 1,4-cycloaddition modes giving rise to three types of carbonyl fragments. 1,1-Diphenyl- and 1-methyl-1-phenylallenes react predominantly by the 1,4-mode. Plausible mechanisms are discussed for the formation of the observed products.

In the dye-sensitized photooxygenation of C-aryl nitrones and hydrazones, short-lived peroxidic intermediates are observed. Their characterization, mechanisms leading to them, as well their decomposition pathways are discussed.

Decomposition of the saturated endoperoxide derived from 6- t -butylfulvene at 1OO°C gives a stable allene oxide which was isolated and characterized by spectroscopy and chemical transformations. The thermal isomerization of the parent unsaturated system is also described and the decomposition mechanisms are discussed.

Saturated fulvene endoperoxides derived from 6-vinylfulvenes prove to be excellent precursors of 5-propylal-substituted 2-cyclopenterones; allene oxides and/or cyclopropanones are postulated as intermediates in these reactions

Saturated fulvene endoperoxides give highly oxygenated compounds upon thermolysis in the presence of acetic acid. Depending on whether the fulvene precursor is 6-mono or 6,6-disubstituted, one obtains either lactol acetates or 1,5-carbonyl compounds, respectively.

The three-carbon ring expansion methodology commences with the preparation of a cyclic allene (C9, C11, C13), readily available from the corresponding cycloalkene via dibromocarbene addition and subsequent treatment with methyllithium. Dichloroketene addition to the cyclic allene regioselectively provides the [2+2] cycloadduct, which is reductively dechlorinated with zinc in methanol. The resulting cyclobutanone is then catalytically hydrogenated; cyclobutanone ring opening is affected with trimethylsilyl iodide; immediate dehydroiodination of the resulting β-iodocycloalkanone with diazabicycloundecane (DBU) provides the corresponding macrocyclic enone. The 15-membered enone was converted to d , l -muscone with (CH 3 ) 2 CuLi.

An unusual peroxide base-promoted isomerization is uncovered. Saturated endoperoxides derived from fulvenes give rise to 2-vinyl-2-cyclopentenones upon treatment with DBU in CH 2 Cl 2 in a one-pot reaction. This methodology is applied to a convenient synthesis of dihydrojasmone. Moreover, functional groups placed on the side chain at C-6 participate in the base-catalyzed isomerizations via conjugate attack at the enone moiety to give 2-cyclopentenones carrying oxygen heterocycles at C-2.

In this study, we have explored the prevention of gastric side effects such as gastric lesions and bleeding while maintaining the high analgesic and anti-inflammatory activities by the derivatization of the carboxylate moiety into amides in [5-chloro-6-(2chloro/fluorobenzoyl)-2-benzoxazolinone-3-yl]acetic acids. We have tested the analgesic and anti-inflammatory activities of the synthesized compounds in vivo by using p-benzoquinone-induced writhing test and carrageenan-induced hind paw edema model, respectively Compounds 3a, 3d, 3e, 3j and 3k showed potent analgesic and anti-inflammatory activities without gastric lesions in the tested animals. Therefore, conversion of the carboxylate moiety into certain amide derivatives generated potent analgesic and anti-inflammatory compounds while eliminating the gastrointestinal side effects. Cyclooxygenase (COX)-selectivity of the active compounds was also investigated by using in vitro human whole blood assay. Compounds 3 a, 3 e, 3 h and 3 k demonstrated selective inhibition of COX-2 to some extent although the inhibitory activity was not very potent.

The saturated endoperoxide derived from 6,6-dimethylfulvene was shown to be a unique source of an allene oxide and a cyclopropanone: inter- and intramolecular trapping experiments provided permissive evidence that such intermediates are indeed operative in the thermal isomerizations of fulvene endoperoxides.