Beatriz Lantaño

Recent Advances in Trifluoromethylation Reactions with Electrophilic Trifluoromethylating Reagents

Electrophilic trifluoromethylation reactions have been the latest approach to achieve the fluoroalkylation of compounds with newly-discovered reagents, such as the Tognis (1-trifluoromethyl-1,2-benziodoxol-3-(1 H)-one), Umemotos (S-(trifluoromethyl)dibenzothiophenium tetrafluoroborate), Yagupolskiis (S-(trifluoromethyldiarylsulfonium salts), Shreeves (S-(trifluoromethyl)dibenzothiophenium triflate), and Shibatas (trifluoromethylsulfoximine salts) reagents. All these reagents produce an electrophilic trifluoromethylating (CF3 (+) ) species that undergoes reaction with nucleophiles. In addition, these latter reactive species (i.e. CF3 (+) ) can undergo electron-transfer (ET) processes affording CF3 (⋅) radicals that expand the scope to substrates other than conventional nucleophiles that can undergo reaction. In this Review, we shall discuss the trifluoromethylation reactions of diverse families of organic substrates of biological interest as a means to comparing the reagents scope and best reaction conditions. Some, though not all, of these reactions require the assistance of metal or organometallic catalysts. Some require additives and catalysts to promote the fluoroalkylation reaction, but invariably all are initiated and carried out by electrophilic trifluoromethylating species.

Silica-supported heteropolyacids as catalysts in alcohol dehydration reactions

Catalysts based on Keggin-type heteropolyacids supported on silica were prepared for their use in dehydration of alcohols in liquid phase. Species present in the catalysts were characterized by diverse physicochemical techniques, disclosing that both molybdophosphoric and tungstophosphoric acids are found with their primary Keggin structure intact. Their catalytic behavior was studied in the dehydration of alcohol of interest for the production of intermediary compounds for fine chemical industries. Specifically, the dehydration of 1,2-diphenylethanol, 1-(3,4-dimethoxyphenyl)-2-phenylethanol and cholesterol was studied. It was obtained a process for the direct dehydration of cholesterol. It was found that the catalysts are very active and selective, also allowing an easy separation from the reaction medium. The same catalysts were used several times without appreciable loss of catalytic activity and after the reaction they showed physicochemical properties similar to those of the original catalysts.

A Formal [3 + 2] Alkene Addition to Benzhydrol Cations. A Practical and Mild Methodology for the Synthesis of Substituted 1‐Arylindanes and Related Compounds

Abstract We report the single step synthesis of several 1‐arylindanes in good yield via a formal [3 + 2] atom cycloaddition. The success of this formal cycloaddition relies on the Lewis acid activation of a bibenzylic alcohol in the presence of an alkene. The cation generated from the alcohol can be trapped by the alkene to afford a new benzylic cation which can then undergoes cyclization leading to 1‐arylindanes with three stereogenic centres.

SILICA-SUPPORTED HETEROPOLYACIDS READILY INDUCE CYCLODIMERIZATION OF STYRENES AND STILBENES

ABSTRACT Heteropolyacids such as molybdophosphoric and tungstophosphoric acids, supported over silica, readily induce cyclodimerisation reactions of styrenes and stilbenes affording a mixture of indane and/or tetraline derivatives with remarkably high efficiency and in reduced reaction time.

ZnI2/NaCNBH3 as an Efficient Reagent for Regioselective Ring Opening of the Benzylic Epoxide Moiety

Abstract In the presence of zinc iodide, sodium cyanoborohydride was found to produce regioselective ring opening of benzylic epoxides in mild reaction conditions.

Synthesis and biological evaluation of novel homochiral carbocyclic nucleosides from 1-amino-2-indanols

New chiral purinyl and 8-azapurinyl carbanucleoside derivatives based on indanol were synthesized from commercial available (1S,2S)-trans-1-amino-2-indanol and (1R,2R)-trans-1-amino-2-indanol using a linear methodology. The antiviral activity and cytotoxicity of these compounds were evaluated against herpes simplex virus type 1 (HSV-1) in Vero cells, bovine viral diarrhea virus (BVDV) in Mardin-Darby bovine kidney (MDBK) cells and hepatitis B virus (HBV) in HepG2 2.2.15 cell line. Three compounds, showed an inhibition of the HBsAg levels similar to reference drug lamivudine. One chloropurinyl nucleoside, derived from the cis-1-amino-2-indanol, was cytotoxic on MDBK cells and it could be a lead for developing anticancer agents.

Transition metal- and organophotocatalyst-free perfluoroalkylation reaction of amino(hetero)aromatics initiated by the complex [(TMEDA)I·I3] and visible light

Radical initiation for the perfluoroalkylation reaction of amino(hetero)aromatics has been accomplished employing the complex [(TMEDA)I·I3] and visible light. This methodology circumvents the use of metal(organo)catalysts and biologically-relevant substrates are easily substituted with RF moieties employing a mild and environmentally benign radical strategy starting from readily-available perfluoroalkyl iodides RFI.

Dehydration of alcohols catalysed by heteropolyacids supported on silica

Keggin type heteropolyacids supported on silica efficiently dehydrated secondary and tertiary alcohols under mild conditions and in good yields to afford the correspondent alkenes.

A Simple Synthetic Route to Pterosin F and Other Pterosins

A simple method for the preparation of pterosin F is described in which the key step involves a tandem reaction of Friedel–Crafts acylation–cycloalkylation between 2,6-dimethylphenethyl chloride and ethyl methacrylate.

Synthesis of benzylidenecycloalkan-1-ones and 1,5-diketones under Claisen–Schmidt reaction: Influence of the temperature and electronic nature of arylaldehydes

ABSTRACT Herein, we present the results of the influence of reaction temperature and the electronic nature of arylaldehydes in the reactions of benzocycloalkan-1-ones and arylaldehydes under classical Claisen–Schmidt condensation conditions. The products obtained, 2-arylidene derivatives of benzocycloalkan-1-ones and/or spiropolycyclic-1,5-diketones through multicomponent reactions, depended on the electronic nature of arylaldehyde and the reaction temperature. Besides, under identical conditions, 2-arylideneindan-1-ones afforded bis-indane-1,5-diketones through a process that involves Michael addition reaction, which is also dependent on the temperature. Theoretical studies using density-functional theory allowed understanding the chemical reactivity and the site selectivity of α,β-enones used in this work through the calculation of global and local electrophilicity on C–β. Both the electrophilicity of C-β and the temperature led the course of reaction toward the formation of aldol condensation, aldol condensation/Michael addition, and aldol condensation/dimerization products. This work is the first to perform the structural and configurational assignments of bis-indane-1,5-diketones. GRAPHICAL ABSTRACT