Catalytic enantioselective synthesis of carbocyclic and heterocyclic spiranes via a decarboxylative aldol cyclization.

The synthesis of a variety of enantioenriched 1,3-diketospiranes from the corresponding racemic allyl beta-ketoestersviaan interrupted asymmetric allylic alkylation is disclosed. Substrates possessing pendant aldehydes undergo decarboxylative enolate formation in the presence of a chiral Pd catalyst and subsequently participate in an enantio- and diastereoselective, intramolecular aldol reaction to furnish spirocyclic beta-hydroxy ketones which may be oxidized to the corresponding enantioenriched diketospiranes. Additionally, this chemistry has been extended to alpha-allylcarboxy lactam substrates leading to a formal synthesis of the natural product (-)-isonitramine.