Hela. Chim. Acta, 48, 1297 (1965). when IIa was heated for a long time at 200-230, the conversion to IVa was~ omplete,~ as well as could be detected by the infrared analysis used. According to the accepted mechani~ m,~~~ the rearrangement of IIa to IVa via the spirodienone intermediate IIIa should be reversible. Although IVa would be expected to be favored in an equilibrium between IIa and IVa, there is one report in the literature which ...
