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.

Synthesis of 1-ethyl-2-methyl-3-arylindanes. Stereochemistry of five-membered ring formation

“…4,10 When 9 was treated with alcohol 11 in the presence of SnCl 4 the same dimer 10 was obtained. In the crude reaction mixture the presence of another diastereomer was not detected.…”

“…Dimerisation in mineral acid medium, 8 with ethyl polyphosphate (EPP), 9 or with silicasupported phosphotungstic or phosphomolybdic acid (TPA/S and MPA/S) 10 of isohomogenol and isosafrole, produces mainly cyclodimers with α configuration, accompanied by the γ stereoisomer in some cases as a minor product. Such cyclodimer type may also be obtained by formal [3+2] cycloaddition of alcohol derived cation and alkene.…”

“…The δ stereoisomer has only been obtained by means of stereodirected synthesis. 13 It has been postulated that both, cyclodimerisation of styrenes in acid medium 10 …”

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.…”

Samarium triflate-catalyzed dimerization of vinylarenes

“…After pioneer work by Bergmann and co-workers, 1 various promoter-mediated synthetic routes have been documented via the intermolecular hydroarylation of vinyl arenes followed by spontaneous intramolecular ring-closure of the resulting dimeric isomers (Scheme 1). They include different metal-free reagents (I2, TFA, aminium salt), [2][3][4][5] transition-metal complexes (In 3+ , Bi 3+ , Ru 3+ -Ru +4 , Pd 2+ /In 3+ , Eu 3+ , Au 3+ , Mo 2+ , Ce 3+ ), [6][7][8][9][10][11][12][13] nanoparticles (MCM-41, Al-SiO2, H3PW12O40/SiO2, Nafion) [14][15][16][17] or other methods. [18][19][20][21] On the basis of observations, attempts to develop new and efficient catalyst systems for the self-dimerization of vinyl arenes are still in demand.…”