Synthesis Optimization of Hydroxymethylnitrofurazone, an Antichagasic Candidate, Using 3(2) Factorial Design

Hydroxymethylnitrofurazone presents in vitro activity against Trypanosoma cruzi. The optimization of the synthesis of this compound was performed through a 3(2) factorial statistical design. Quadratic model produced the best response surface predicting a maximum yield (82%) close to the center design point with a seven hours reaction and a 1:1.5 (NF:K(2)CO(3)) ratio.

Synthesis of alpha,beta-unsaturated aryl esters via Heck reaction of unsymmetrical aryl tellurides

A variety of alpha,beta-unsaturated aryl esters were prepared by the direct reaction of unsymmetrical aryltellurides and ethyl acrylate, catalyzed by PdCl(2) via a Heck cross-coupling reaction. (C) 2009 Elsevier Ltd. All rights reserved.

SYNTHESIS AND RETRO AZA DIELS-ALDER REACTION OF SOME NEW ISOQUINUCLIDINE DERIVATIVES

N-Benzyl- and N-(alpha-methoxycarbonylethyl)-2,4,6-triphenyl-1,2-dihydropyridines were submitted to Diels-Alder reactions with maleic anhydride or N-phenylmaleimide yielding, diastereoselectively, the corresponding endo-anti adducts. These novel isoquinuclidines showed to be resistant to N-alkylation or N-protonation, undergoing an unexpected fragmentation via a retro aza Diels-Alder process.

Practical synthesis of chiral beta-telluro amines by ring-opening reaction of aziridines

A set of chiral beta-tellurium amines and their selenium and sulfur-containing derivatives have been efficiently synthesized in good to excellent yields via the ring-opening reaction of chiral aziridines by chalcogen nucleophilic species. (C) 2008 Elsevier B.V. All rights reserved.

Synthesis of the C7-C24 fragment of (-)-Macrolactin F

An enantioselective and convergent synthesis of the C7-C24 fragment of Macrolactin F was achieved from four main fragments. A hydrotelluration/transmetalation sequence was used to install the E,Z diene present in the molecule, while a hydrozirconation/transmetalation sequence was used to connect two advanced intermediates. (C) 2008 Elsevier Ltd. All rights reserved.

Organotellurides as precursors of reactive organometallics

Reaction of organotellurides with easily available organometallics leads to a fast and clean tellurium/metal exchange reaction, allowing the preparation of a range of functionalized organometallics with C-sp(3), C-sp(2), and C-sp hybridization carbanionic centers. Some synthetic applications of the tellurium/metal exchange reactions are discussed.

Synthesis of substituted alpha,beta-unsaturated delta-lactones from vinyl tellurides

A new approach for the synthesis of alpha,beta-unsaturated delta-lactones, a unit present in many natural products with interesting biological activities is described. The approach was based on the use of a vinyl telluride, and it is complementary to the methods using ring-closing metathesis. The sequence was performed in good overall yield with retention of the Z-double bond geometry. (C) 2011 Elsevier Ltd. All rights reserved.

Synthesis of Tetrahydrofurans by Cyclization of Homoallylic Alcohols with Iodine/Iodine(III)

Tetrahydrofuran derivatives can be obtained by cyclo-functionalization of homoallylic alcohols bearing a terminal double bound by using [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser`s reagent) in the presence of a catalytic amount of 12 (20 mol %) in MeOH under mild conditions. This transformation is an overall 5-endo-trig cyclization, which occurs by two different pathways. The first is a 4-exo-trig cyclization followed by ring expansion, whereas the second is an electrophilic addition followed by a 5-endo-tet cyclization.

Microwave-Assisted Derivatization of Cellulose in an Ionic Liquid: An Efficient, Expedient Synthesis of Simple and Mixed Carboxylic Esters

Microwave (MW)-assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low-energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1-allyl-3-methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW-assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DS(ethanoate) > DS(propanoate) > DS(butanoate). The values of DS(pentanoate) and DS(hexanoate) were found to be slightly higher than DS(ethanoate). This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate-based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 134-143, 2010

Efficient synthesis of selenol esters from acid chlorides mediated by indium metal

This article describes an efficient and easy one-pot route for the synthesis of a wide range of selenol esters from acyl chloride with diselenides in the presence of indium metal. A variety of functional groups can be tolerated within the diorgano diselenide and the acyl chloride coupling partner. (C) 2009 Elsevier Ltd. All rights reserved.

Synthesis of 4-iodopyrazoles: A Brief Review

The selective incorporation of halogen into organic molecules provides a challenge to academic and industrial research. This microreview presents an overview of the available methodologies for the synthesis of 4-iodopyrazoles, valuable precursors for the selective construction of highly functionalized organic molecules of synthetic and biological importance.

Catalytic enantioselective arylations: boron to zinc exchange as a powerful tool for the generation of transferable aryl groups

The transmetalation between boron and zinc is of great importance for application in organic synthesis, since it allows the formation of new carbon-carbon bonds between organometallic units and electrophiles. The direct arylation of aldehydes or more scarcely ketones, in a catalytic, enantioselective manner using chiral catalysts has been described recently. The enantiomerically enriched diarylmethanols obtained in these reactions are valuable precursors for important bioactive molecules. This review provides a synopsis of this ever-growing field and highlights some of the challenges that still remain.

Highly efficient palladium-catalyzed Suzuki-Miyaura reactions of potassium aryltrifluoroborates with 5-iodo-1,3-dioxin-4-ones in water: an approach to alpha-aryl-beta-ketoesters

The high efficient palladium-catalyzed Suzuki-Miyaura reactions of potassium aryltrifluoroborates 3 with 5-iodo-1,3-dioxin-4-ones 2a-b in water as only solvent in the presence of n-Bu(4)NOH as base is reported. The respective 5-aryl-1,3-dioxin-4-ones 4a-n were obtained in good to excellent yields. The catalyst system provides high efficiency at low load using electronically diverse coupling partners. The obtained 2,2,6-trimethyl-5-aryl-1,3-dioxin-4-ones were transformed into corresponding alpha-aryl-beta-ketoesters 6 by reaction with an alcohol in the absence of solvent. (C) 2009 Elsevier Ltd. All rights reserved.

Functionalization of (2S)-Isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones by a Suzuki-Miyaura Cross-Coupling Reaction Using Aryltrifluoroborate Salts: Convenient Enantioselective Preparation of alpha-Substituted beta-Amino Acids

A simple protocol for the Pd(OAc)(2)-catalyzed cross-coupling reaction of 1-benzoyl-(2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones with potassium aryltrifluoroborates was developed. The reaction is performed at 110 degrees C with a ligand-free catalyst. In all cases, complete conversion of the 1-benzoyl-(2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones and aryltrifluoroborates into the C-C coupling products was observed within 30-360 min. It is noteworthy that a large variety of groups present in the potassium aryltrifluoroborates (-CF(3), -OMe, -SEt, -CN, -CHO, -Cl, -Cbz, -NCbz, -OH, -CO(2)H) could be tolerated. Hydrogenation of the endocyclic double bonds in the Suzuki-Miyaura products followed by acid hydrolysis afforded highly enantioenriched alpha-aryl-substituted beta-amino acids.

alpha-Arylation and Alkynylation of Cyclic alpha-Iodoenones Using Palladium-Catalyzed Cross-Coupling Reactions with Trifluoroborate Salts

An expeditious synthesis of alpha-aryl- and alpha-alkynylcyclo-hexenones is described and illustrated by palladium-catalyzed cross-coupling reaction of cyclic alpha-iodoenones with potassium aryltrifluoroborate salts. This procedure offers easy access to alpha-arylated and alkynylated cyclohexenones functionalized with electrondonor and -acceptor substituents in good yields.