Stereoselective Synthesis of (<i>E</i>)-4-Alkylidenecyclopent-2-en-1-ones by a Tandem Ring Closure−Michael Addition−Elimination

Abstract

Reaction of (Z)-1,4-diketones with various functionalized nitroalkanes in the presence of DBU gives 4-alkylidenecyclopent-2-en-1-ones with E selectivity. A cyclopentadienone intermediate is probably formed by intramolecular aldol condensation, and this reacts with a nitroalkane giving a Michael addition-elimination.