No abstract

Conjugated dienes, properly activated by electron-withdrawing groups on both ends, are shown to be suitable substrates for phosphine-promoted organocatalytic processes. Their reactions with imines, under phosphine catalysis, afford a new and efficient synthetic approach to functionalized 3-pyrrolines.

The synthesis of highly functionalized heterocyclic spiranes has been carried out by [3 + 2] cyclizations between allenoates and enones, under phosphine catalysis. Excellent enantioselectivity levels (ees up to 99%) have been attained in Ferro-PHANE-promoted cyclizations of this class, leading to chiral sulfides with unprecedented spiranic structures. The corresponding sulfoxides have been obtained then via a subsequent, highly diastereoselective oxidation of the prostereogenic sulfur centre.

International audienceA new synthetic approach to hexahydroisoindol-4-ones is reported, based on the formal [3+2] cyclization reaction between N-arylsulfonylimines and cyclic conjugated dienes, under phosphine catalysis. Key substrates are 3-vinylcyclohex-2-enones with electron-withdrawing substituents (ester, amido, cyano, phosphoryl and keto groups) on the exocyclic double bond, which afford the three atom synthons for the construction of the pyrroline ring. Total syn stereoselectivity is observed in these annulations. The scope of the reaction has been demonstrated and mechanistic issues are considered, based on deuteration experiments and DFT calculations