Intramolecular Hydroalkoxylation of Non‐Activated CC Bonds Catalysed by Zeolites: An Experimental and Theoretical Study

Abstract

The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Brønsted acid sites (ca. 0.2 mmol g(-1)) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Brønsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications.

Intramolecular hydroalkoxylation catalyzed inside a self-assembled cavity of an enzyme-like host structure

“…The application of weaker acids on the other hand often requires the use of over-stoichiometric amounts. 13 Alternative catalytic approaches include the utilization of Lewis super-acids like Al(OTf) 3 14 and Ca(NTf 2 ) 2 , 15 transition metals, 16 zeolites 17 and Amberlyst H-15. 18 In the context of supramolecular catalysis, Bergman, Raymond and Toste investigated the intramolecular hydroalkoxylation of activated hydroxy olefins inside a supramolecular host using an encapsulated gold catalyst.…”

Simple metal salts supported on montmorillonite as recyclable catalysts for intramolecular hydroalkoxylation of double bonds in conventional and VOC-exempt solvents

“…The reaction can be promoted or catalysed by a large variety of Brønsted or Lewis acids under homogeneous conditions 1,2 or with heterogeneous catalysts such as zeolites. 3,4 The methodology has proven its utility in the synthesis of fine chemicals including bioactives [5][6][7] and fragrant molecules, 8,9 for example (Fig. 1).…”

Porous Catalytic Systems in the Synthesis of Bioactive Heterocycles and Related Compounds

“…Large-pore zeolites such as BEA/37.5 or FAU/15 were the most efficient catalysts in the reaction (Scheme 8) [59]. Large-pore zeolites such as BEA/37.5 or FAU/15 were the most efficient catalysts in the reaction (Scheme 8) [59].…”