Facile construction of novel polycyclic ring systems using a metallocarbenoid-induced cyclization of acetylenic diazo carbonyl compounds

[GRAPHICS] The Rh(II) catalyzed reaction of diazo 2-propynyl maolonamic acid ester der ivatives produce furo[3,4-c]furans in excellent yield. The methodology was applied to the synthesis of several polyheterocyclic systems by first gener ating a 5-alkoxy substituted furan and then allowing it to undergo a subseq uent intramolecular Diels-Alder cycloaddition. Ring opening of the resultin g cycloadduct is followed by deprotonation to furnish a rearranged keto lac tone.