DFT studies on the allylation of styrene oxide catalysed by indium nanoparticles (InNPs)

Organometallic compounds provide a source of nucleophilic carbon centers which can react with electrophiles to form new carbon-carbon bonds. In particular, allyl-indium species are known to react with various electrophiles, such as carbonyl compounds, to generate homoallylic alcohols. Epoxides are good electrophiles that could react with organometallic compounds. The intrinsic tension of these cyclic systems makes them very reactive starting materials, giving access to more complex products through the regiochemical controlled ring-opening. With this aim, the allylation of epoxides with indium powder has been reported by several research groups.

In this work, indium nanoparticles (InNPs) has been prepared through a simple methodology, under mild reaction conditions, by fast reduction of indium(III) chloride with lithium sand and a catalytic amount of 4,4’-di-tert-butylbiphenyl (DTBB), in THF as solvent, at room temperature and under nitrogen atmosphere. The freshly prepared InNPs, were employed as catalysts for the ring-opening allylation reaction of styrene oxide with allyl or prenyl bromides, working both at room temperature and under reflux of ACN or THF. Moreover, the reactions were studied by the adding the reactants under both Grignard and Barbier conditions.

To provide a clearer understanding of the experimental results, computational analyses by using the Gaussian09 program were performed. DFT calculations were executed with the B3LYP functional, and LanL2DZ pseudopotential. All the possible reaction paths for the formation of the different alcohol products were calculated, achieving very good correlation between the experimental and computational results.