ALPHA-PYRONES .3. SYNTHESIS OF 5,6-DIHYDRO-1 H-BENZO[C]-QUINOLIZIN-1-ONES FROM 6-(2-NITROSTYRYL)-2H-PYRAN-2-ONES

The 6-(2-nitrostyryl)-2H-pyran-2-ones 1 were reduced with hydrogen ove r Pd/C at room temperature and atmospheric pressure giving the ,2,3,4- tetrahydro-2-quinolinylidene-2-pentenedioic acid derivatives 2 which w ere converted, without isolation, into the 5,6-dihydro-1H-benzo[c]quin olizin-1-ones 4 in refluxing acetic anhydride. When alpha-aminoacids 2 were treated with acetic anhydride at room temperature oxazolones 3 w ere isolated, while by heating quinolizines 4 were found. Compounds 3 were transformed into 4 in refluxing acetic acid or anhydride.