Syntheses of 2-Carbomethoxy-5,10-dimethyl-6,8-bisdehydroannulenone, a Potential Precursor of Macrocyclic Azulene Analogues, and (Z)- and (E)-14-Carbethoxy-2-carbomethoxy-5,10-dimethyl-6,8-bisdehydrofulvenes

Article abstract of DOI:10.1021/jo00162a017

The synthesis of 2-carbomethoxy-5,10-dimethyl-6,8-bisdehydro<13>annulenone (15), a potential precursor of macrocyclic azulene analogues, and its elaboration into (E)- (19) and (Z)-14-carbethoxy-2-carbomethoxy-5,10-dimethyl-6,8-bisdehydro<13>fulvene (20) is reported.The 1H NMR spectrum of 15 is interpreted to indicate that in the average conformation the C-12,13 double bond is not coplanar with the ring, and a reappraisal of the conformation of 2,5,10-trimethyl-6,8-bisdehydro<13>annulenone (16b) is made.The <13>fulvenes 19 and 20 show little or no paratropicity and serve as model systems for the estimation of paratropicity in 15 and related systems.