Stereocontrolled construction of tricyclic furan and pyrrolyl derivatives via tungsten-mediated [3+2] cycloaddition and intramolecular Diels-Alder reaction

Vinylpropargyl tungsten complexes were prepared to comprise a tethered unsaturated ester designed for intramolecular Diels-Alder reaction. Treatment of these vinylpropargyl tungsten complexes with aldehydes and imines in the presences of BF3.OEt2 resulted in a [3+2] cycloaddition to give 2,5-dihydrofuran and pyrrole derivatives. Hydrodemetalation of these tungsten heterocyclic compounds was achieved with Me3NO in CH3CN and the resulting furyl and dihydropyrrolyl dienes undergo highly diastereoselective intramolecular Diels-Alder reaction to give tricyclic furan and pyrrolyl derivatives efficiently. This method provides a short stereoselective synthesis of tricyclic furan and pyrrole derivatives.