Pyrrolidinyl-camphor derivatives as a new class of organocatalyst for direct asymmetric Michael addition of aldehydes and ketones to β-nitroalkenes

Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl-camphor derivatives (7a-h). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical αα-disubstituted aldehydes to β-nitroalkenes. When this asymmetric transformation was cata-lyzed by organocatalyst 7f, the desired Michael adducts were obtained in high chemical yields, with high to excellent stereoselectivities (up to 98:2 diaste-reomeric ratio (d.r.) and 99% enantiomeric excess (ee)). The scope of the catalytic system was expanded to encompass various aldehydes and ketones as the donor sources. The synthetic application was demonstrated by the synthesis of a tetrasubstituted-cyclohexane derivative from (S)-citronellal, with high stereoselectivity.