A deconjugative alkylation/Diels-Alder cycloaddition strategy to synthesize 2-substituted bicyclic scaffolds

Abstract

Knoevenagel adducts derived from α,β-unsaturated aldehydes and a malonic acid derivative can undergo deconjugative alkylation using dienophile-functionalized alkyl iodides. The single step reaction is two-fold significant: (a) The electron-deficient diene (α,β-unsaturated aldehyde Knoevenagel adduct) is deconjugated from the esters, resulting in an electronically neutral diene and (b) tethers the diene and dienophile, which allow for intramolecular cycloaddition to bicyclic systems bearing a malonic acid derivative at the 2-position. The sequence thus converts simple reagents into natural product relevant bicyclic scaffolds. We also disclose an unexpected Diels-Alder cycloaddition/aromative CC cleavage reaction that results due to the malonate's location at the 2-position.