Direct Asymmetric Synthesis of Quaternary Carbon Centers via Addition-Elimination Process: Nitroolefination of α-Substituted δ-Lactones

Article abstract of DOI:10.1021/ja00202a037

The reactions of chiral nitro enamines 2a-c with zinc enolates 4-6 of α-substituted δ-lactones afforded α,α-disubstituted δ-lactones with a high ee through an addition-elimination process.The best results were obtained with the reaction of 2c with 5.Michael-type addition of the enolate onto the nitro enamine is kinetically controlled and decides the absolute stereochemistry of the product.A cyclic transition model is proposed to rationalize the S-selectivity.