Pyrrolidines quaternary chiral centers

Some heterocyclic systems such as tetrahydrofuxan, tetrahydropyran, thiophene, and pyrrolidine are foimd in a wide range of biologically active compounds. Hydroformylation of these heterocyclic olefins provides a potential synthetic route for the synthesis of these targets (Scheme 11) [93,94]. Asymmetric hydroformylation of a-methylene-y-butyrolactone using the cationic Rh(I)-(l )-BINAP complex as a catalyst is also reported to give an aldehydic lactone containing a quaternary chiral center in up to 37% ee [95]. 

They have developed direct asymmetric synthesis of quaternary carbon centers via addition-elimination process. The reactions of chiral nitroenamines with zinc enolates of a-substituted-8-lactones afford a,a-disubstituted-6-lactones with a high ee through addition-elimination process, in which (5)-(+)-2-(methoxy methy l)pyrrolidine (SMP) is used as a chiral leaving group (Eq. 4.96).119 Application of this method to other substrates such as a-substituted ketones, esters, and amides has failed to yield high ee. 

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