96. P. Müller, J.-P. Schaller,
    “Synthesis of cycloproparenes via aromatization of 7-Oxanorbornenes with Low-Valent titanium”
    Helv. Chim. Acta 1989, 72, 1608-1617.

1H-Cyclopropa[b]naphthalene 3c and the 2,7-diphenyl-substituted derivative 3a have been synthesized via cycloaddition of the appropriate isobenzofurans 1a and 1b to 1-bromo-2-chlorocyclopropene and aromatization of the adducts with low-valent Ti. The same procedure afforded the 2,7-dimethyl-H-cyelopropa[g]isoquinoline (15), but failed for the parent azacompound. Reaction of adducts of furans to 1-bromo-2-chlorocyclopropenes with low-valent Ti produced mixtures of cyclopropabenzenes 19 and 1,6-dihalogeno-1,3,5-cycloheptatrienes 18. The latter could be converted to cyclopropabenzenes with BuLi.

DOI : 10.1002/hlca.19890720721 

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