The tin salt Sn(NTf2)4 (Tf=trifluoromethanesulfonyl) is an efficient catalyst for the selective and ring‐size‐specific cycloisomerization of highly substituted 1,6‐dienes to give six‐membered‐ring carbocycles (see scheme; X=C(CO2Et)2, C(CO2Me)2 C(CN)(CO2Et), etc.). This is the first Lewis acid catalyzed cycloisomerization of this type of substrate.

Das Zinnsalz Sn(NTf2)4 (Tf = Trifluormethansulfonyl) erwies sich als wirksamer Katalysator in der selektiven und ringgrößenspezifischen Cycloisomerisierung von hoch substituierten 1,6‐Dienen zu carbocyclischen Sechsringen (siehe Schema, Beispiele für X: C(CO2Et)2, C(CO2Me)2, C(NC)(CO2Et)). Es handelt sich um die erste Lewis‐Säure‐katalysierte Cycloisomerisierung solcher Substrate.

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This review deals with the application of Lewis super acids such as Al(III), In(III), and Sn(IV) triflates and triflimidates as catalysts in the synthesis of fragrance materials. Novel catalytic reactions involving C-C and C-heteroatom bond-forming reactions, as well as cycloisomerization processes are presented. In particular, Sn(IV) and Al(III) triflates were employed as catalysts in the selective cyclization of unsaturated alcohols to cyclic ethers, as well as in the cyclization of unsaturated carboxylic acids to lactones. The addition of thiols and thioacids to non-activated olefins, both in intra- and intermolecular versions, was efficiently catalyzed by In(III) derivatives. Sn(IV) Triflimidates catalyzed the cycloisomerization of highly substituted 1,6-dienes to gem-dimethyl-substituted cyclohexanes bearing an isopropylidene substituent. The hydroformylation of these unsaturated substrates, catalyzed by a Rh(I) complex with a bulky phosphite ligand, selectively afforded the corresponding linear aldehydes. The olfactory evaluation of selected heterocycles, carbocycles, and aldehydes synthesized is also discussed.

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