The reaction of 6,8-dioxabenzocycloheptenes 3 or 8,10-dioxacycloocta[de]naphthalenes 5 [easily prepared from the dibenzylic diols 1 and 4,respectively,and a carbonyl compound] with an excess of lithium and a catalytic amount of DTBB (2.5 mol %) in THF at temperatures ranging between -78 and -60 °C leads,after hydrolysis with water,to the corresponding homobenzylic alcohols 6 and 7,respectively.Cyclization of compounds 6 and 7 under acidic conditions (85% H3PO4 for diols 6 and p-TsOH for diols 7) affords the expected isochromans 8 and naphthoxepines 9,respectively.
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