On the Catalysis of the Cycloisomerization of 1,6‐Dienes with Tin(IV) Salts: The Important Role of a Water Molecule

Abstract A diene cycloisomerisation reaction catalysed by tin(IV) triflimidate 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 regeneration 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 SnL 4 , L=triflate (OTf), triflimidate (NTf 2 ) and a chlorosulfonate model (OSO 2 Cl). The diastereoselectivity observed in the cycloisomerisation 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.