Synthesis of Cycloproparenes via Aromatization of 7-Oxanorbornenes with Low-Valent Titanium

Article abstract of DOI:10.1002/hlca.19890720721

1H-Cyclopropanaphthalene 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-1H-cyclopropaisoquinoline (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.