George Majetich

Application of commercial microwave ovens to organic synthesis.

Abstract Commercial microwave ovens have been safely used to dramatically reduce the reaction times (at comparable yield) of Diels-Alder, Claisen, and ene reactions. Significant solvent effects were also observed.

The Taiwaniaquinoids: A Review†‡

A comprehensive overview of the taiwaniaquinoid family of natural products is presented. A summary of the isolation, biosynthesis, and biological activity of these compounds is followed by a discussion of various synthetic strategies to the skeletal framework and a detailed discussion of 12 published syntheses of members of this family. This review covers the literature from the discovery of the first taiwaniaquinoid in 1995 until June 2009.

Applications of microwave-accelerated organic synthesis☆

Abstract A comparison of microwave vs conventional heating is presented for a variety of Diels-Alder reactions, ortho-Claisen rearrangements, ene reactions, alkyl bromide preparations, Finkelstein reactions, oxidations, esterifications, hydrolyses, Williamson ether syntheses and other common organic transformations. In general, microwave-promoted reactions proceed with significant decreases in reaction times and in comparable chemical yield.

Studies on tandem ene/intramolecular Diels-Alder reactions

Abstract Tandem ene/intramolecular Diels-Alder reactions of 1,4-cyclohexadiene and mono - or di -activated acetylenes are optimized. Analogous reactions with disubstituted bicyclohexa-1,4-dienes regioselectively produce highly functionalized tetracyclic adducts.

Multispectral identification of chlorine dioxide disinfection byproducts in drinking water

This paper discusses the identification of organic disinfection byproducts (DBPs) at a pilot plant in Evansville, IN, which uses chlorine dioxide as a primary disinfectant. Unconventioal multispectral identification techniques (gas chromatograpby combined with high- and low-resolution electron-impact mass spectrometry, low-resolution chernical ionization mass spectrometry, and Fourier transform infrared spectroscopy) were used to identify more than 40 DBPs in finished water at a chlorine dioxide pilot plant in Evansville, IN. Treatment variations included the use of liquid versus gaseous chlorine dioxide and the use of residual chlorine

Determination of capsinoids by HPLC-DAD in Capsicum species.

Capsicum fruits contain a newly discovered phytochemical called capsinoids. Because little is known about the quantities of these compounds in both sweet and pungent pepper fruits, a high-performance liquid chromatography (HPLC) method was developed to identify and quantify the capsinoids (naturally present E-capsiate and dihydrocapsiate) utilizing fruit obtained from a variety of Capsicum spp. in the U.S. Department of Agricultures Capsicum germplasm collection. Capsinoids were extracted with acetonitrile, filtered, and analyzed using an HPLC system equipped with a C(18) monolithic column, gradient pump, and diode array detector. The elution solvents were acetonitrile and water (60:40) with an isocratic flow rate of 1.0 mL/min. Forty-nine samples representing distinct morphotypes of four cultivated species ( C. annuum var. annuum, C. annuum var. glabriusculum, C. baccatum , C. chinense , and C. frutescens ) contained detectable levels (11-369 microg/g) of E-capsiate quantified at a wavelength of 280 nm. Nine of the E-capsiate-containing samples also had dihydrocapsiate (18-86 micro/g). Gas chromatography with a mass spectrometry detector (GC-MS) confirmed the presence of these compounds in the Capsicum spp.

A Direct Stereoselective Synthesis of (±)-14-Deoxyisoamijiol☆

Abstract A 16-step total synthesis of (±)-14-deoxyisoamijiol is reported featuring an intramolecular Sakurai reaction to stereospecifically construct the dolastane skeleton.

Allylsilane initiated garbocyclizations

Abstract The intramolecular conjugate addition of an allylic anion, generated from a allylsilane moiety, with various Michael acceptors is reported.

Chemoselectivity in the conjugate addition of allylsilane to Michael acceptors

Abstract The allylic carbanion species generated by treatment of allylsilane with fluoride ion undergoes highly chemoselective conjugate addition to a series of Michael acceptors for which alternative known allylation procedures proved less general.

Hydride-promoted demethylation of methyl phenyl ethers

Abstract Solutions of L-Selectride or SuperHydride in refluxing THF efficiently deprotect methyl phenyl ethers. L-Selectride is the more effective reagent, while electron-poor arenes work best. Unlike other hydride sources, these reagents permit ether cleavage without the reduction of aryl halides.