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Félix Rodríguez

Publications and source records attributed to Félix Rodríguez.

At least 19 recordsLinked to original sources
PubMed2005

IPy2BF4-mediated rearrangements of 1,2-difunctionalized compounds and olefins.

Acetal derivatives are easily obtained from 1,2-difunctionalized compounds by a new reaction mediated by IPy2BF4 with a mechanism based on a 1,2-migration of aryl or alkyl groups. A new oxidative rearrangement reaction of olefins is also described. Moreover, when this metal-free protocol is applied to cyclic olefins, interesting ring-contraction reactions are observed. The new methodologies described here are a clean and efficient alternative to known strategies that make use of potentially toxic metallic complexes.

Journal Article↗
PubMed2005

[W(CO)5]-catalyzed endo- or exo-cycloisomerization reactions of 1,1-disubstituted 4-pentyn-1-ols: experimental and theoretical studies.

The [W(CO)5]-catalyzed cycloisomerization reaction of 1,1-disubstituted 4-pentyn-1-ol derivatives has been studied from both, an experimental and theoretical point of view. Three different catalytic systems have been evaluated {preformed [(thf)W(CO)5], [W(CO)6]/excess Et3N, and [W(CO)6]/2 mol % Et3N]. We have found that the reaction proceeds to give the formal endo- or exo-cycloisomerization products depending on the amount of Et3N used and on the substitution along the alkyl chain of the starting alkynol. The theoretical study allowed us to find the mechanisms of the reactions which explain the formation of the formal endo- or exo-cycloisomerization products.

Catalysis↗
PubMed2005

Coupling reactions of zirconocene complexes and heterosubstituted alkenes.

This tutorial review surveys recent advances in the field of zirconium promoted coupling reactions of unsaturated molecules (and/or organolithium compounds) and heterosubstituted alkenes. This reaction has recently emerged as a powerful tool in organic chemistry to access a variety of synthetically useful building blocks not easily available by other methods. In particular, three different reaction pathways are discussed: i) the reaction involving alkyne-zirconocene and aryne-zirconocene complexes which allows access to dienyl and aryl zirconocene complexes; ii) the reaction of alkene-zirconocene complexes and enol ethers which has shown to be highly dependent on the structure of the enol ether used, allowing the synthesis of simple vinyl zirconocenes or multicomponent coupling products, and; iii) the reaction involving imine-zirconocene complexes which supposes a new entry to allylic amines.

Journal Article↗
PubMed2005

Solvent-assisted new reaction pathways for the (THF)W(CO)5-promoted endo- and exo-cycloisomerization of 4-pentyn-1-ol: a theoretical investigation.

New solvent-assisted mechanistic routes were located for the (THF)W(CO)5-promoted endo- and exo-cycloisomerization of 4-pentyn-1-ol using the B3LYP/6-31G (with the LANL2DZ relativistic pseudopotential for W) theory level. A mixed model was used by explicitly including a THF molecule as a component of the reactive system and taking into account the effect of bulk solvent by means of the PCM-UAHF method. This THF molecule plays a crucial role by making the endo route leading to the cyclic carbene complex the most favorable one because of an important catalytic effect. These new mechanisms allow a satisfactory rationalization of experimental facts.

Journal Article↗
PubMed2004

Stereoselective synthesis of pentacarbonyl(3-oxa-2-bicyclo[3.1.0]hexylidene)- and pentacarbonyl(cyclopropylmethoxymethylene)tungsten compounds on the route to cyclopropane-gamma-lactones and -carboxylates.

The diastereoselective synthesis of pentacarbonyl-3-oxa-2-bicyclo[3.1.0]hexylidene- and pentacarbonyl(cyclopropylmethoxymethylene)tungsten compounds 4 and 9 by the reaction of lithiated oxazolinyloxiranes 2 and 8 and Fischer carbene tungsten complexes 3 is described. A mechanism for the formation of 4 and 9 is reported as well as their oxidation to cyclopropane-gamma-lactone 13 and -carboxylate 14.

Journal Article↗
PubMed2004

Total synthesis of the Fusarium toxin equisetin.

A short stereoselective synthesis of the Fusarium toxin equisetin, a potent inhibitor of HIV-1 integrase enzyme is described, using as the key step a stereoselective intramolecular Diels-Alder reaction of a fully conjugated E,E,E-triene with a trisubstituted gamma,delta-unsaturated beta-ketothioester.

Fusarium↗
PubMed2004

Synthetic approach to substituted cyclopropanes based on the coupling reaction of lithiated chloroalkyloxazolines with Fischer carbene complexes.

Regioselective addition of lithiated oxazoline 2a, easily available from 2-(1-chloroethyl)-4,4-dimethyl-2-oxazoline 1a (LDA, THF, -98 degrees C), to alpha,beta-unsaturated Fischer carbene complexes 3 afforded cyclopropylcarbene complexes 4 as sole diastereoisomers. Exposure of carbene complexes 4a-c (M = Cr) to air and sunlight gave cyclopropane carboxylate derivatives 5a-c. A plausible mechanistic explanation is proposed. Moreover, when lithiated oxazoline 2b was generated from 1b in the presence of the carbene complex 3a,b, the oxazolinylcyclopropane carboxylates 6a,b formed as a 1:1 mixture of diastereoisomers. Chiral lithiated oxazoline 2c added regioselectively and diastereoselectively to chromium complexes 3a,b and to tungsten complexes 3d,e, leading, after oxidation of the metal fragment, to esters 7a,b with good diastereoselectivity (dr = 4:1). The reaction of lithiated oxazoline 2d with chromium complex 3b and tungsten complex 3e proceeded less diastereoselectively, furnishing, in both cases, after oxidation, the ester 7c as a 3:2 diastereoselective mixture.

Journal Article↗
PubMed2004

Zirconium-mediated cross-coupling of terminal alkynes and vinyl bromides: selective synthesis of cyclobutene and 1,3-diene derivatives.

A diastereoselective synthesis of 1,3-butadiene or cyclobutene derivatives by a zirconium-mediated reaction of alkenyllithium compounds and vinyl bromides is reported. The key steps involve the generation of zirconocene-alkyne complexes from haloalkenes and subsequent coupling with alkenyl bromides. Thus, formally the process supposes the cross-coupling reaction between a terminal alkyne and an alkenyl bromide. Moreover, the use of butyl vinyl ether instead of vinyl bromide as the unsaturated system allows an alternative access to different 1,3-butadiene regioisomers.

Journal Article↗
PubMed2004

Zirconium-mediated coupling reactions of amines and enol or allyl ethers: synthesis of allyl- and homoallylamines.

An easy and efficient zirconium-mediated synthesis of allylamines from simple amines and enol ethers is described. This strategy also allows the synthesis of amino alcohol derivatives containing a Z double bond in their structure when 2,3-dihydrofuran is used. Simple conventional modification of these amino alcohols leads to 2-substituted piperidine derivatives. By applying this approach, a formal total synthesis of the alkaloid coniine is easily achieved from a protected butylamine. Finally, the zirconium-mediated reaction of amines and allyl phenyl ether furnishes homoallylamines or amino ethers depending on the structure of the starting amine.

Journal Article↗
PubMed2003

Total diastereofacial selective iodofunctionalization of terpene derivatives based on Ipy2BF4.

Acetonides 1, easily obtained from simple terpenes, react with bispyridine iodonium (I) tetrafluoroborate (Ipy(2)BF(4)) and tetrafluoroboric acid in the presence of nucleophiles to give the corresponding adducts 2 with complete regio and diastereofacial control. Acetonides 1 containing a properly located phenyl or benzyloxy group easily undergo iodocyclization to furnish compounds 3 and 4.

Magnetic Resonance Spectroscopy↗
PubMed2003

Acid-catalyzed Grob fragmentation reactions of acetonides derived from terpenes.

[reaction: see text] Acetonides derived from different terpenes undergo Grob fragmentation by treatment with a catalytic amount of acid, triflic acid, or boron trifluoride, giving aldehydes containing a cyclopropane or cyclobutane ring with good yields and complete diastereoselectivity. The structure and the stereochemistry of the starting acetonide have a crucial influence on the reaction course.

Journal Article↗