José M. Aguirre

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.

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.

Structure and stereochemistry of cyclodimers obtained by acid treatment of trans-stilbenes and of N-1,2-diarylethylamides

The reaction of trans-stilbenes and N-1,2-diarylethylamides with ethyl polyphosphate affords indanes and tetralins with three stereogenic centres. The structural and configurational assignment of the cyclodimers is based mainly on the NMR and MS data. A possible transition state for the reaction is discussed.

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

Effect of methoxyl groups on the NMR spectra: configuration and conformation of natural and synthetic indanic and tetralinic structures: Effect of methoxyl groups on the NMR spectra of indanic and tetralinic structures

Here, we studied the influence of the methoxyl groups attached at C‐7 and C‐2′ of natural and synthetic 1‐arylindanes on the chemical shift of the signal of bibenzylic hydrogen and carbon atoms and J1,2 coupling constants. This influence was also analysed in natural 1‐aryltetralins and related compounds that possess methoxyl and/or hydroxyl groups bound at C‐8 and C‐2′. The methoxyl groups attached at C‐7 in indanes or at C‐8 in tetralins produce a deshielding signal at H‐1 and shield at C‐1 and a strong decrease in the value of J1,2 due to the pseudoequatorial location adopted by the aryl group bound at C‐1, avoiding an ‘A1,3 strain’. Furthermore, compounds with hydroxyl or methoxyl groups in C‐2′, in the absence of substituents of C‐7 or C‐8, present a strong deshielding signal at H‐1, strong shield of the C‐1 signal and a decrease in the value of J1,2. This is attributed to the stereoelectronic effects of the methoxyl or hydroxyl groups, which we have called ‘Asarone effect’. NOESY experiments were conducted to confirm the configuration and conformation of some of the compounds included in this work. This study shows that both effects, A1,3 strain and Asarone effect, must be taken into account when the structure of natural indanes and tetralins is analysed by using 1H‐NMR and 13C‐NMR spectra. Copyright

trans-2-Benzoyl-1-phenylindan

We have been performing extensive research on the synthesis and configurational effects of substitution in the fivemembered ring of indan derivatives (Aguirre et al., 1998; Aguirre et al., 1999; Alesso et al., 2002; Alesso et al., 2003). In particular, we have been seeking alternative routes through stereoselective synthesis for indan and tetranilic derivatives via condensation of aryl ketones. As part of these results, the compound 2-benzoyl-1-phenylindan, (I), could be synthesized in acid solution and isolated as a single product. The trans configuration was assigned by NMR studies in CDCl3 solution (Mufato et al., 2002).

Synthesis of Indanes Via a [3+2] Cycloaddition

The acid -promoted [3+2] cycloaddition of alkenes with benzhydrylic alcohols afford products in good yield and with remarkable stereoselectivity.