Synthesis of Highly Functionalized Chiral Benzopyrano[3,4-c]pyrrolidines Bearing Five Contiguous Stereogenic Centers
摘要:
A chiral bis(imidazolidine)pyridine-Cu complex smoothly catalyzed the asymmetric [3+2] cycloaddition reaction of alpha, beta-unsaturated ester-containing nitroalkenes with imino esters to give endo-pyrrolidine products in a highly enantioselective manner while maintaining the alpha, beta-unsaturated ester functionality. Subsequent intramolecular diastereoselective cyclizations of the obtained pyrrolidine products were accomplished by treatment with KF/Al2O3 in toluene/EtOH (4:1) to give highly functionalized benzopyrano[3,4-c]pyrrolidines bearing five contiguous stereogenic centers.
Under control: A formal [4+1]/[3+2] cycloaddition cascade of sulfurylides and alkene‐tethered nitroolefins has been developed, and provides an efficient synthesis of fused polycyclic heterocyclic compounds in good to excellent overall yields with excellent diastereocontrol (see scheme). A catalytic asymmetric variant of this reaction has also been disclosed.
intramolecular Rauhut–Currier reaction of linear bis(enones) has been achieved via double activation catalysis of thiols and phase transfer substances, furnishing both enantioenriched cyclohexene and cyclopentene derivatives (up to 95% ee). Furthermore, the desymmetric version of prochiral substrates was developed under similar catalysis, producing the frameworks bearing an additional tertiary or even quaternary