Microwave-Assisted One-Pot Telescoped Synthesis of 2-Amino-1,3-thiazoles, Selenazoles, Imidazo[1,2-a]pyridines, and Other Heterocycles from Alcohols.

Primary and secondary alcohols have been converted into 2-amino-1,3-thiazoles under microwave irradiation, employing trichloroisocyanuric acid (TCCA) as a dual oxidant and chlorine source, TEMPO as a co-oxidant, and thiourea. Secondary alcohols underwent a single-stage, one-pot conversion process, while primary alcohols required a two-stage, one-pot procedure. Both transformations were completed within minutes (25-45 min). The versatility of this protocol extends to the synthesis of other heterocycles, including 1,3-selenazoles, 2-aminoimidazoles, imidazo[1,2-a]pyridines, quinoxalines, and hydrazino thiazoles by replacing thiourea with the appropriate surrogates.

Ultrasound-promoted synthesis of a copper-iron-based catalyst for the microwave-assisted acyloxylation of 1,4-dioxane and cyclohexene.

A copper-iron-based catalyst has been prepared by a low-temperature co-precipitation and sonication method. The use of high-energy ultrasound reduces the time required for the preparation process from one workweek to one day with respect to the catalysts obtained by conventional coprecipitation and thermal treatment methods. The resulting material has been characterized at compositional, textural, structural, and chemical levels by ICP-AES, BET, SEM-EDS, XRD, TEM, and FTIR among other techniques. The material shows catalytic activity in the acyloxylation reaction of 1,4-dioxane and cyclohexene under microwave irradiation. In parallel with the optimized catalyst synthesis, the use of microwaves allowed for a substantial improvement in the outcome of the reaction in terms of cleanliness, yield, and time.

Copper-Catalyzed Microwave-Expedited Oxyphosphorylation of Alkynes with Diethyl Phosphite and t-Butyl Hydroperoxide Synthesis of Densely Functionalized Phosphonylated Indenones.

Treatment of alkynes with diethyl phosphite and t-butyl hydroperoxide in the presence of [Cu(MeCN)4]BF4 under microwave irradiation produced the oxyphosphorylation of the triple bond, giving rise to the corresponding ß-ketophosphonates in moderate-to-good yields. When the triple bond was conjugated to a carbonyl group bearing an aromatic ring, it led to the cyclization of the resulting ketone intermediate, producing eventually different phosphonylated indenones.

Microwave-Enhanced Coupling of Carboxylic Acids with Liquid Ketones and Cyclic Ethers Using Tetrabutylammonium Iodide/t-Butyl Hydroperoxide.

The oxidative coupling of carboxylic acids with liquid ketones and cyclic ethers has been accomplished in minutes using t-butyl hydroperoxide in the presence of tetrabutylammonium iodide under microwave irradiation in the absence of a solvent. In addition to drastically shortening the reaction times, the use of microwaves resulted, in general, in yields equal to or higher than those obtained by conventional heating.

Acyloxylation of 1,4-Dioxanes and 1,4-Dithianes Catalyzed by a Copper-Iron Mixed Oxide.

The use of a copper-iron mixed oxide as a heterogeneous catalyst for the efficient synthesis of α-acyloxy-1,4-dioxanes and 1,4-dithianes employing t-butyl peroxyesters is reported. The preparation and characterization of the catalyst are described. The effect of the heteroatoms and a plausible mechanism are discussed. The method is operationally simple and involves low-cost starting materials affording products in good to excellent yields.

Acyloxylation of cyclic enones: synthesis of densely oxygenated guaianolides.

The α'-acyloxylation of cyclic enones with linear carboxylic acids is described. The reaction is promoted by KMnO4 in the presence of a carboxylic acid and its corresponding carboxylic anhydride. The optimization of the reaction has been carried out using the statistical methodology known as design of experiments. The optimized reaction conditions have been evaluated in terms of substrate scope and compatibility with different functional groups. The methodology has been applied to the synthesis of densely oxygenated guaianes and guaianolides.

A phenylpropanoid, a slovenolide, two sulphur-containing germacranes and Ca2+-ATPase inhibitors from Thapsia villosa.

A phenylpropanoid 1, a slovenolide 2, and two germacranes bearing a methylthiopropenoate moiety, 3 and 4, along with twenty known metabolites have been isolated from the roots of Thapsia villosa var. villosa L. The structures of two known phenylpropanoids 5 and 6 have been corrected. Compounds 7 and 8 showed activity as potential inhibitors of the sarco- and endoplasmic Ca(2+)-dependent ATPases (SERCA) pump. Compounds 9, 10 and 11 increased significantly the cytoplasmic free calcium concentration ([Ca(2+)](c)) in human platelets in a concentration-dependent manner.

Toward the synthesis of thapsigargin: enantioselective synthesis of 7,11-dihydroxyguaianolides.

[reaction: see text] The enantioselective synthesis of a 7,11-dihydroxyguaianolide bearing the stereochemistry present in thapsigargin, a potent and selective inhibitor of the Ca(2+) SERCA-ATPase pumps, is described. Starting from (+)-dihydrocarvone, the synthesis presents two key steps. The first one involves the photochemical rearrangement of a gamma,delta-unsaturated ketone eudesmane into the corresponding guaiane. The second step consists of the regioselective oxidation of an unprotected tetrahydroxylated ketone to provide a dihydroxylactone with the required stereochemistry.

Phenylpropanoids from Thapsia transtagana.

Five phenylpropanoids have been isolated from the roots of Thapsia transtagana. Their structures have been elucidated by spectroscopic means.

Transtaganolides A-D: novel metabolites from Thapsia transtagana.

Four novel and unusual C-19 compounds from Thapsia transtagana, named transtaganolides A-D, have been isolated. Their structures were established by physical methods, including X-ray analysis of transtaganolides A and B. This is the first time that a 7-methoxy-4,5-dihydro-3H-oxepin-2-one ring has been found in a natural product. [structure: see text]

Allylic oxidation of alkenes catalyzed by a copper-aluminum mixed oxide.

A strategy for the allylic oxidation of cyclic alkenes with a copper-aluminum mixed oxide as catalyst is presented. The reaction involves the treatment of an alkene with a carboxylic acid employing tert-butyl hydroperoxide as the oxidant. In all cases, the corresponding allylic esters are obtained. When L-proline is employed, the allylic alcohol or ketone is obtained. The oxidation of cyclohexene and valencene has been optimized by design of experiments (DoE) statistical methodology.

Recent advances in the synthesis of sesquiterpenolides from Umbelliferae.

A review of our latest developments in the synthesis of sesquiterpenolides isolated from plants of the Umbelliferae family is presented.

Sesquiterpenes from Thapsia nitida var. meridionalis and Thapsia nitida var. nitida.

Nine new eudesmanolides (1-9), two new guaianolides (12 and 13), and a new germacrane (10), along with a previously reported guaianolide (11), have been isolated from the roots of Thapsia nitida var. meridionalis. Thapsia nitida var. nitida also afforded compound 13 along with a new guaianolide (14). The structure of 13 was confirmed by X-ray crystallographic analysis. Compounds 1, 2, and 11-14 have been tested as potential inhibitors of the sarco- and endoplasmic Ca2+-dependent ATPases (SERCA) pump. None of them showed significant activities.