An Easy, Stereoselective Synthesis of Hexahydroisoindol‐4‐ones under Phosphine Catalysis.

A new synthetic approach to hexa hydroisoindol - 4-ones is reported, based on the formal (3+2) cycli zation reaction between N-arylsulfonylimines and cyclic conjugated dienes, under phosphine catalysis. Key substrates are 3-vinylcyclohex-2-enones with electr on- withdrawing substituents (ester, amido, cyano, phos phoryl and keto groups) on the exocyclic double bond, whic h 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 be en demonstrated and mechanistic issues are considered, based on deuteration experiments and DFT calculations.