Syntheses of 6,7-Benzotropolones by a Sequence of Acylation (or α-Hydroxyalkylation/Oxidation), Ring-Closing Metathesis, and Hydrolysis/β-Elimination.

Starting from ortho -bromostyrenes, 12 6,7-benzotropolones were synthesized in 3 or 4 steps. Br/Li exchanges provided the respective ortho -lithiostyrenes. The latter were acylated by a Weinreb amide, if unhindered, or hydroxyalkylated by an aldehyde, if hindered (an oxidation ensuing thereafter). Acetonide-containing benzannulated nonatrienones resulted. Ring-closing olefin metatheses converted them into acetonide-containing benzocycloheptadienones. Treatment with aq. HCl caused hydrolyses followed by β-elimination reactions giving 6,7-benzotropolones.