International audienceA diene cycloisomerisation reaction catalysed by tin(IV) triflimi- date is studied by using DFT computations. It is proposed that the mechanism does not involve the direct addition of the tin(IV) cation to a double bond because the catalyst regenera- tion step would be energetically unfeasible. We show that a water molecule may play a decisive role to enable the smooth completion of the catalytic cycle. The proposed active catalyst is thus a hydrated triflimidate salt. The hydrolysis and hydration energies are computed for three ligands of SnL4, L= triflate (OTf), triflimidate (NTf2) and a chlorosulfonate model (OSO2Cl). The diastereoselectivity observed in the cycloisomeri- sation is discussed in light of the transition-state geometries. The hypothesis of hidden Brønsted acid catalysis is discussed and ruled out on the basis of new experimental results

The auto-oxidation of trans-1,2-disiloxybenzocyclobutene was found to be very efficient, giving endo-peroxide in quantitative yield. Each step of the mechanism of spin-forbidden addition of triplet oxygen O2((3)Σg) was studied by both EPR/spin trapping and theoretical studies.

Pseudopotentials for hybridized atoms are extracted and combined. The study focuses on sp(2) carbon atoms and their combination to give rise to a π electronic system. As electrons of interest are treated explicitly, any ab initio method can be used, thus, configuration interaction methods and time-dependent density functional theory are used and compared. All electron and pseudopotential calculations are in good agreement for electronic transition spectroscopy (0.2 eV difference), geometrical parameters (error of 0.8 pm), and reaction energies.