Synfacts 2007(11): 1145-1145  
DOI: 10.1055/s-2007-991292
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Fused Coumarins via Cycloaddition Reactions

Contributor(s): Victor Snieckus, Jignesh J. Patel
C. E. Henry, O. Kwon*
University of California, Los Angeles, USA
Further Information

Publication History

Publication Date:
23 October 2007 (online)

Significance

Intramolecular phosphine-catalyzed allene/alkene [3+2] cycloadditions of allenoates B and D to produce substituted coumarin adducts C and E, respectively, is reported. A single diastereo­isomer of C was obtained in good to excellent yield. Both EWG and EDG were compatible with the reaction conditions. Interestingly, nitrostyrenyl D gave [3+2] annulation product E in THF using PPh3 in moderate yield with a minor amount of F while D follows a [4+2] annulation pattern to form the nitronate F as major product under benzene/P(4-FC6H4)3 conditions. The ni­tronate F was further utilized in the 1,3-dipolar cycloaddition with alkenes to afford isomeric tetracyclic coumarin derivatives G in excellent yields.