Fresh routes to derivatives of cyclohepta[de]naphthalene

2,3-Dihydrocyclohepta[de]naphthalene-1,4-dione (1) is formed by cyclising methyl 3-(1-naphthoyl)propionate. It forms only monoacetals, gives a hemiacetal salt with alkali, and can be dehydrogenated to a quinone (14) that undergoes ring-contraction to a phenalenone (15) on acetalisation.Acenaphthylene traps dichloroketen inefficiently, allowing formation of the dimer (19) of tetrachloroallene, but dechlorination of the acenaphthylene adduct (16) followed by opening of its cyclobutanone ring with acid gives cyclohepta[de]naphthalen-2(1H)-one (21). This and the isomeric cyclohepta[de]naphthalen-1(2H)-one (23) obtainable from the dione (1), were reduced to alcohols with the object of preparing cyclohepta [de] naphthalene (26) by ester pyrolysis.